I'm looking to run a cleric starting at level 8 in a game we've had going for some time.  We don't have a healer/support in the group, so I'd like to fill that role.  We currently have a Battlemaster Fighter (pole arm master/sentinel glass cannon - he's had some absolutely terrible HP rolls), Way of Shadows Monk, and Conjuration Wizard (though she plays like an evocation wizard /  complete agent of chaos).

I find myself leaning towards a support or backlines cleric, since we have two strikers up front, but could be convinced to play a front liner pretty easily.

Which domain would you all recommend for the party?  Debating between life, light, arcana, or grave and I am being terribly indecisive.

Thanks!

The Cleric chassis is already great at healing and support all by its self. That means you can treat the domain as flavor and just play what you think would be more fun to role play without having to stress about mechanics. All your options are fun and make for great stories. You are pretty safe no matter what you pic so just enjoy.

If this just gives you 'analysis paralysis' try this: Think of the character you want to play and describe that character using 3 other characters form movies, comics, books, online games, history, etc. Imagine that character now, and just pick a domain that fits your feel of it. (ex: If I described my character as a mix of Iron Man, Captain America and Thor -  Id could make a Forge Cleric who is a heroic smith that is super patriotic. Other people could take the same concept and make a Tempest domain cleric that crafts his own weapons and armor. Be creative and have a good time!)

I agree with Ajexton, you're going to be a solid healer no matter which domain you choose, but some domains are definitely more focused on support while others offer frontline boosts. If all you're worried about is keeping the proverbial health bars full, you can't go wrong with Life domain. One benefit of that domain that isn't talked about much is their domain spells. Yes, they're all from your spell list, but they're mostly spells you would be preparing as a healer anyway. Since you get them for free, it leaves slots open in your "spells prepared" list to try other spells from the Cleric list that you might otherwise not have room for. Grave domain has some good combat emergencies for when things get dire. Being able to use Spare The Dying at range and as a Bonus Action is great in a pinch. Getting max healing when you're bringing someone back from zero is also quite good. And being able to turn what could be a devastating crit into a regular hit at just the right moment can be crucial. Arcana can be a really fun choice, I played one in Storm King's Thunder and really liked it. Being able to grab a couple of Wizard cantrips can be good for utility, but it also lets you pick a couple of damage cantrips so you have reliable ways to hurt the bad guy without burning spell slots that you might want to save for healing. 

I would also highly recommend looking over the list of deities in your game's world. Life domain generally works fine with any deity, even the evil ones(bad guys need healing too). But maybe there's a specific deity in your world that appeals to you, or that you think would allow for some interesting roleplay. Are some gods outlawed, like in Wildemount? Is there a god who's been largely forgotten, and only recently have followers begun to reappear in the world? Is there a god who might be particularly interested in whatever grand story your DM has in mind? If you're just looking to play a healing machine you're free to do so, it's your game. But being a Cleric has lots of story potential, too.

As someone who loves the Arcana Cleric (I always play Half-Elves) I want to recommend the Arcana Cleric (obviously).

Looking at your party what you seem to be missing is someone to play music to cheer people up, and a Rogue.

So, an Arcana Cleric, with the Entertainer background, proficiency in lute, so you can lute while not fighting. Using the rules on Page 125 PHB, switch out proficiency in Disguise Kit for proficiency in Thieves' Tools. Perhaps he's an escape artist as part of his show.

As a Half-Elf I'd start with 8/16/14/10/16/10, with proficiency in acrobatics and performance (from Entertainer) insight and persuasion (from Cleric) and stealth and perception (from Half-Elf). Tool proficiencies in thieves' tools and instrument: lute (from modified Entertainer). Then of course I'd add +4 Wisdom because you're starting at level 8.

Studded leather and a shield, with a dagger as your melee weapon (don't worry you won't use it). From Wizard take the Shocking Grasp and Chill Touch cantrips. Although Fire Bolt is stronger than Chill Touch, fire damage is resisted more often than necrotic damage. Thanks to Powerful Spellcasting you're doing 2D8+5 damage with Shocking Grasp and the same with Chill Touch. You're also a Cleric with all the good Cleric spells, and out of combat you can play your lute in taverns for food and lodgings, saving you money.

Of course there are any number of different backgrounds to choose with different skills to take. Perhaps your cleric is more interested in making medicines, so take tool proficiency with herbalism kit and the medicine skill, perhaps as an Outlander.

I'm an arcana fan too, but honestly, my recommendation is light.  Light is simply amazing and is far more useful than arcana until level 17.

There's a cleric for any kind of character you want to play, so really it is all up to you.

Damage clerics: Light, Tempest, death

Damage negation and utility: Grave and Arcana

Pure healer: Life

Subterfuge and social: Trickery and Knowledge

Tank: War and Forge

Nature cleric is probably the one cleric subclass that I would say is underwhelming, but I can see how it can be useful in other campaigns as well.  Especially when the party lacks a druid and you find yourself in the wilderness quite a bit.

Thanks all, ended up going with Arcana, devout of Mystra.  Partly because it interested me and partly because my wife plays as the wizard who keeps creating chaos in the group (she summoned a Barlgura during a dinner at the governor's mansion recently, ended up ripping the governor in half in front of all his guests - turns out he was innocent too).  The arcana cleric fits into the group build wise but also as an advisor for her - which I do all the time anyway since she frequently asks me for help with her spells.

So far, enjoying the character quite a bit!  Last session I used the Arcane Eye domain spell to save our party a lot of trouble and put us in a potentially beneficial position (political power struggle going on in the campaign, I was able to scout out a route through the sewers to free a number of hostages).  I like following Mystra as well since I don't feel the need to try and convert people, I just tell/teach them about the weave and how to respect it or control it, if they have the aptitude.

That does sound like it fits into your campaign well, which is good. 

There are certainly a great variety of clerics.

Clerics are very interesting characters because they develop in a different unlike most character.