Looking through the Twilight cleric, let's talk about the changes made from UA to release. In the UA, the Twilight Cleric is all about controlling the darkness in encounters. They can create dim light as well as magical darkness that so many creatures have problems with. At release, the Twilight cleric is useful for....err.... giving you a shady spot to sip lemonade?

Items are from the published versions, the strikeout text is from the UA.

Twilight Domain spells

3rd Moonbeam (Darkness), See Invisibility (Invisibility)

9th Circle of Power, Mislead (Dream)

Moonbeam in place of Darkness? That's a horrible trade. Moonbeam is a highly situational small area denial spell. Need to make a vampire think twice about entering a 10ft wide hallway? Moonbeam's your spell. Any other time? Pretty useless. Darkness has way more utility both in and out of combat.

See Invisibility vs Invisibility isn't a bad swap. It goes with the "This Cleric has really good eyesight" that the rest of the domain proclaims.

Dream is pretty meh for a fifth level spell. I mean best case is you use it on a BBEG a few nights leading up to a big fight. Mislead is much more fitting for a Trickery domain cleric. Something like Dawn would be more on-brand.

Eyes of Night:

Darkvision to 300 feet (Unlimited), can be shared with [WISMOD] creatures for 60 minutes (10 minutes), recharges on long rest or by expending any spell slot to recharge it (UA version was recharge on long rest only).

These changes I like. limiting the darkvision range removes the arguments of "I could totally see that dragon flying over the town 3 miles away at night". The extended time limit and recharge make this ability much more useful in caves and the Underdark.

Channel Divinity: Twilight Sanctuary

1d6+cleric level temporary hit points (1d8 hit points)

Another good change. 1d8 was pretty strong in the early levels. Dialing it back but adding the cleric level lets it remain relevant at higher tiers of play.

Steps of Night (Steps of the Brave)

Nothing (Advantage on saving throws vs being frightened)

Gain flying speed equal to your walking speed for 1 minute (Until the end of your next turn), Can be used [Proficiency Bonus] of times per long rest (Unlimited)

Kinda sucks losing a boon without gaining anything. Thought this domain was supposed to be a stalwart protector of the darkness?

Why in the name of the gods is this cleric flying? Drawing on "the mystical power of night to rise into the air" seems like a poorly written homebrew.

Divine Strike

extra 1d8 radiant damage (psychic damage)

Makes sense to me.

Twilight Shroud (Midnight Shroud)

You and your allies have half cover while in the sphere created by your Twilight Sanctuary. (Whenever you cast the darkness spell using a spell slot, you can choose a number of creatures that you can see (including yourself) equal to your Wisdom modifier (minimum of one). The chosen creatures can see through the darkness.)

Yeah, I hit 17th level! Can't wait to be able to see through magical darkness! ...what do you mean I get half cover instead? I can get that at first level from a large rock!

In summary, the banner abilities of this domain were removed. Ouch.

It doesn't seem so bad. No Darkness Spell seems kinda meh but Moonbeam is pretty cool I think. Dawn is on the Cleric spell list anyway.

The next 2 were made better.

Steps of the Night seems pretty much a boon , too. Flying for 1 Minute is much much better than for a round. It means you'll have the bonus action free from then on. The Advantage is kinda sad but is pretty specific, too.

The lvl 17 Ability isn't so much a thing for me. 17 is pretty far up there. But sure that seems to be a bit of a nerf. Seems more like twilight to me now tho.

Still seems extremely OP, particularly the channel divinity.  It's very heavily front loaded for those looking for the heavy armor dip...why not get 300 ft dark vision and advantage on initiative to go with it.  Moonbeam is more thematically appropriate than darkness.

really nothing there to "ouch" over.  It was massively OP before.  Now it's just OP.

The Channel Divinity was massevly buffed! Even at level 2 it's better than UA (1d6+2 vs 1d8). 

And fly without concentration? This is one of the strongest clerics, hands down. Perhaps the strongest.

There were already a number of domains that give heavy armor, so I'm not sure why that's an issue.

Quote from Xalthu >>

There were already a number of domains that give heavy armor, so I'm not sure why that's an issue.

 No, that alone isn't. But the Darkvision 300 feet and advantage on initiative at will for one char on top of it? Perhaps that's an issue. And at level two you get on of the best (defensive) Channel Divinity options...

Don't get me wrong. I love the twilight cleric. But I think it's one the strongest official clerics (not counting zeal domain from planeshift pdf).

Quote from Xalthu >>

There were already a number of domains that give heavy armor, so I'm not sure why that's an issue.

 heavy armor isn't the problem.  Dipping cleric to get heavy armor is pretty common.  The issue is the quanity and quality of EXTRA things you get at first level.

if I am going to make a dip for heavy armor, there are a /lot/ of classes you can pick from to do it.  I'm going to take the choice that gives me the most bang for my buck.  let's say I am going to play a wizard, but I want to dip for heavy armor.  I could go fighter or cleric with the proper domain, and get the heavy armor I want.  I decide I want cleric instead of fighter because cleric is a full caster and won't slow down my spell slot progression.

So, I look at clerics.  Off the top of my head two heavy armor choices come to mind, War and Twilight.  War gives me the heavy armor I want, martial weapons, and the ability to make a bonus action attack with a melee weapon when I take the attack action.  That last ability is useless, so War is basically /only/ giving me the heavy armor I want.

twilight on the other hand gives me the heavy armor i want, and the same martial weapons that war does (that I don't care about).  it also gives me superior darkvision, the ability to grant my superior darkvision to my teammates, an advantage on my initiative rolls (or to someone else in my party if I want them to go first).  Those are all pretty good picks, so if I want heavy armor, picking twilight as my dip over war is a no-brainer option.

I was actually thinking of life and tempest and forge. Life is not going to be so great for the wizard from your example (though, actually, the more people around with cure wounds, the better), but a tempest cleric being able to blow back melee attackers is very strong for a wizard And forge making that heavy armor you just got +1 is also very strong (especially since any you find in treasure hoards is just logically going to the fighter or paladin first)
Personally, I’d rather have either of those over dark vision, that’s what torches or a light cantrip are for. (I know, you can’t see as far with those, but how often does that really matter that your in complete darkness and want to see something 300 feet away) And advantage on initiative is nice, but imo really only matters in the first round — it’s not nothing, and can make a difference, but by round 3, it won’t matter anymore. 
And the domain spells for twilight are pretty meh. Sleep is next to useless after 1st level. Faerie fire can be good, but uses your concentration. 
compare that to thunder wave for a tempest, or getting identify for free from forge, twilight gets less useful spell choices. 
I’m not saying twilight isn’t powerful, I just don’t think it so completely outclasses other domains. Seems pretty in line with other choices to me. I guess we’ll have to wait for people to have time to actually play one. 

Spell choices I don't factor in /generally/ because I assume a 13 wis will make most of them have crappy DC.  That said, generally speaking I am a big faerie fire fan. and value it over thunderwave, which I can also get as a wizard spell, but with a better save.  Agree that sleep is useless, although in the levels I can actually use it, i can prepare it as a cleric spell and be as useful as preparing it with a wizard slot.  Assuming a 13 wiz, the cleric spells I am going to pick are mostly baseline cleric staples such as healing and bless spells which don't require an attack roll or saving throw.

You make a solid point on forge.  Life and Nature had already come to mind for me along with War, and I crossed both off as being just as poor as War.  I'd forgotten tempest, but still prefer twilight (unless I am scribe trying to make channel divinity max damage lightning balls).  Forge as you point out is a strong contender, but generally I value darkvision higher than the extra +1 because most games I am in require a bit of sneaking about and light sources can compromise that.  the +1 from forge though IS highly solid.

Order domain also gets heavy. A skill proficiency, but if we continue this wizard/cleric multiclass, they've probably dumped cha, so you won't get a lot of use from it. And letting allies attack every time you buff or heal them is pretty good, but probably not exciting for a mainly wizard multiclass who won't be buffing as much. So again, another one people probably wouldn't take just for the armor.

Which, I realize, re-enforces your already good points, twilight is a strong contender for a 1-level dip. Just, like I said, I don't think its the only good choice.

Really, though what you're talking about is min/maxers. Since I'd guess most (certainly not all) people who dip for a single level are more worried about squeezing every +1 they can out of a page full of stats, rather than letting a character evolve and develop. And people who play that way are always going to find optimal exploits from any set of options, so I don't worry too much about them abusing the system. I just assume they will, and I move on with my life. I generally don't play with them, but if that's how they have fun, more power to them.

I haven't looked too closely at order domain.

I am personally a bit of a min-maxxer.  My group is a wide variety...one person min-maxes enough to make me shake my head.  Others like fun, quirky characters that are often sub-optimal.  Pre-Tasha's, as long as I avoided overt powergaming moves, the price for serious cheese was usually a pretty high buy in cost...enough to deter me from wanting to try it.  For example, devil's sight.  Before, it was a 2 level buy in, which is a significant price to pay for spell progression.  Now, it's a feat that I can get at level 1.  For me, that means I have to reign myself in (because I don't want to steal the spotlight from my teammates) and make what I think are poor decisions, or, crap all over their characters.  Before, the price of outstripping people made it harder to do it.  Now, it's easy to make stronger characters which will make encounter building harder.  Powercreep is a cascading effect, and Tasha's in general, brings it in spades.

Twilight cleric...just makes me shake my head.  the 1 level dip is bad enough with what you get.  2 levels gets you that channel divinity that looks very overpowered from where I sit.  You play a straight twilight cleric and that CD is simply hard to beat, especially at low levels.  Thinking about having a cleric that could do that in the campaign I am in right now, it would have a HUGE difference.  That's a lot of THP, every round when CD is up.  Steps of night?  Comparable to Storm sorc.  I can't complain much about that.  Strong, but not OP.  Divine strike?  Meh.  I dislike melee clerics so generally I think divine strike sucks.  I'd rather have potent cantrip, but DS is par for the course on a martial cleric.  Twilight shroud?  Not sure how much use that will be at 17.   The first two levels though, are imo, ludicrious as a package.

I love being a cleric. My currant cleric is elven Zanthia Liadon. One time during combat, I litterally melted someone using a nat 20 on the level one version of inflict wounds

I'm personally very sad to see that they lost Darkness and gained Moonbeam. Moonbeam is just bad, even if it's thematic. Darkness was generally useful and you could make an interesting build using the new invocation feat for Devil's Sight. Sadly that's gone now. 

In all honesty, the Twilight Cleric didn’t lose Darkness.  You’d just have to prepare it instead of it being always on tap.  It simply makes sense to give domains access to more spells from outside the normal Cleric list.

Quote from FinalMax >>

In all honesty, the Twilight Cleric didn’t lose Darkness.  You’d just have to prepare it instead of it being always on tap.  It simply makes sense to give domains access to more spells from outside the normal Cleric list.

 Darkness isn't a cleric spells. The Twilight Clerid did in fact lose Darkness.

One thing I really like, though it isn't really a change from the UA version I think, is that your Channel Divinity can overcome magical darkness. It isn't a spell, so it is not dispelled by the Darkness Spell.

I'm new (again) to D&D and we are starting a new campaign using Tasha's ... my DM and I talked about me revisiting an elven cleric character lost (captured) 30 years ago.  Nice thing about elves, they in theory are still around.  And yes, given we are using the point buy system, the DC for spells is a big factor.  I'm excited about giving the twilight cleric a spin as it fits with the character's backstory.

I'd like tips on how to effectively use faerie fire.  :)

Thanks!

Try to use it on targets with low dex saves.  Be careful with your positioning; you don't want to hit your friends with it.  Use it if you think an enemy might turn invisible.  You'll not be ble ot use any other concentration spells if you cast Faerie Fire.  Usually bless is going to be a better bet for you, but sometimes Faerie Fire is the right pick.

Get your wisdom as high as you can to make your spells harder to resist. 

You lose invisibility but keep greater invisibility? Somebody goofed!