The updated trigger conditions on Spirit Guardians have made it even more powerful!  Because it now triggers additionally when the emanation enters a creature's space, a caster can more easily "double-dip" on opponents that have trouble moving out of it by approaching and remaining in range, damaging them twice per round.  They can repeat this by backing away and moving up again, damaging opponents on the caster's turn, and then letting it trigger on the end of the enemy's turn if they can't move.  Unlike Moonbeam (which has the same updated trigger conditions), Spirit Guardians moves with the caster so is much easier to re-apply on locked-down enemies.  Moonbeam at least requires the caster's whole action to move.

I'm not a fan of this change on its own. I'd prefer it if the ongoing damage occurred at the start of the caster's turn instead of the end of the enemy's turn; then it would trigger once per round unless enemies came closer and ended their turn closer too.

[Edit a few minutes later]  In fact, the additional change of having it trigger "whenever the Emanation enters a creature’s space" makes it a ton more dangerous, like a supercharged Ashardalon's Stride, also a third level spell.

Ashardalon's Stride deals anyone 1d6 fire damage if you pass within 5 feet of them, no save.

Spirit Guardians deals only your enemies 3d8 radiant/necrotic damage if you pass within 15 feet of them, Wis save for half.

You're drawing enemy-only AOE streaks on the battlefield every turn.  If you can get any sort of movement boost (Monk/Rogue dip?), that streak can get quite large.

Upcast to 7th level, this deals almost as much damage as Fire Storm but is repeatable every turn just by running around.

Have you considered: "A creature makes this save only once per turn."

Quote from Felix6557 >>

Have you considered: "A creature makes this save only once per turn."

Correct, you can't back-and-forth it several times on your own turn (you never could), but you're essentially a seven-square-wide field of radiant damage moving around the battlefield, and if you end your turn within 15 feet of someone and they're unable to leave your aura — say you've got them against a wall and they can't escape with their halved-to-15-feet movement — they take the damage twice each round instead of the once per round in 2014 rules.

This combines well with the new non-concentration Invoke Duplicity:

Cast Spells. You can cast spells as though you were in the illusion’s space, but you must use your own senses.

Move. As a Bonus Action, you can move the illusion up to 30 feet to an unoccupied space you can see that is within 120 feet of yourself.

They don't take the damage twice each round. The spell clearly states they only make the save once per turn. If they start their turn in the area of effect nothing happens and they only make the save if they're still in it at the end of their turn. 

Edit: I'm mixing up turn and round. Ignore me.

Which would be twice in the round.

However the bigger problem with once per turn damage is that your allies can pick you up and drag you around like some kind of murder ball. If you have 4 party members and each one hands you off to the next one then moves away from the enemies and back again that's 4+ saves per round across multiple enemies.

Divine Lawnmower.

I think it should just specify one save per round. They seem to have copied the wording from the new Moonbeam but only the caster can move the Moonbeam so it's not exploitable in the same way.

Once per round is roughly the same power level as it was, and is still plenty strong.

[exasperated lawyer sigh]

It has been 10 years. You know what people use this for and what every single table argues about. Why? Why could you not write clear language that makes it obvious whether or not creatures make saves WHEN it is first cast? Especially since Moonbeam got this (very intuitive and reasonable) treatment? Now we must argue and google mid-game for another decade. Here, I'll redline it for you:

Any other creature’s Speed is halved in the Emanation and when the Emanation enters a creature’s space (including when you first cast it) and whenever a creature enters the Emanation or ends its turn there, the creature must make a Wisdom saving throw.

There. Now we don't have to fight. And to head off any replies arguing this is not how it is intended to work, it is wildly unintuitive that the spell does nothing to creatures standing next to you when you cast it, but DOES immediately force saves on a creature standing 20 ft from you that you walk towards on the same turn after casting it. So easy to have worded it clearly. They gotta get the legal department in there to edit for clarity...

I don't like house ruling things too much BUT I will be for sure house ruling that spells like this can only 'pulse' ONCE per creature per combat round. This silly game play of people readying movement to trigger the pulse multiple times and then have an ally grapple and move them to trigger it again is not creative, its abusive.  

Using push and pull effects to move the bad guys INTO the spell effect is awesome. Having the caster move to force the effect on bad guys is sweet! Dancing around the field to trigger the effect more then once a combat round because of poor wording is lame. 

Think about what type of energy you want to bring to the tables you play at, people that try to trigger this effect through weird movement gimmicks have abusive player tendencies imo. 

Sigh...... does this trigger when it is first cast? I know the 2014 version wasn't supposed to, but that's not how people played it.

They make a save only once. That doesn't necessarily mean they aren't affected multiple times. One save, but lots of 3d8 effects. Step forward, the edge hits them, boom. Step back. Step forward again, edge hits them again, boom. 

How does is work while mounted now? The emination is 15 ft but doesn't your space become the space of your mount? So it's now a 20ft radius spell on a horse. Is that right?

I would say the radius becoming larger because you are mounted is clearly unintended. 

But if the horse (or an otherwise large caster) casts it then everything within 15 ft of the horse is effected. 

This is the difference between an emanation and a spherical area of effect.  Think of them as being like a consequence of being too close.  

@EdwardDolan

This doesn't work because the damage comes solely from the save. The description of the spell specifies that besides the reduced movement speed, the only thing that happens whenever a creature is inside its emanation is that it must make a save once per turn. Upon making the save, damage is dealt.

In other words, the spell's effect is the save, not the damage.

That's true. 

The exploit comes from the phrase "they only make this save once per turn." On another party member's turn or on their turn they can take damage again. So you can play rugby with the cleric and cause the damage multiple times per ROUND.

Yep, that's correct. And it makes no sense conceptually, because it's not like combatants actually follow a turn order; to an outside observer every creature's turn unfolds simultaneously within the six second span that is a round. So the fact that this spell can be exploited like that unless your DM changes it to work once per round like it was probably intended to makes it feel very janky and immersion breaking.

Not sure about these games of rugby people are talking about with a cleric? 

Most clerics wear armor, have a shield and are carrying about 50+ pounds of gear making total weight of anywhere I guess around 300+ pounds.  Now add that 300+ pounds to the weight the rugby player, attempting to carry the cleric, is already carrying and check the rules glossary to see if the total weight equals carrying capacity or less for their strength. Correct, even that 18 strength rugby player (270lbs carrying capacity) is inching the cleric up the battle field a whole 5 feet - weaker members  with strength 10 or less can't even move him.

Anyway, have fun playing rugby if that is what you think you should be trying to do with your turn, the DM allows it, and your table enjoys the theatre of mind of what is happening...

Totally overpowered now 

First session with it in use the party had the monk with Grappler Feat move the bad guy in and out of it - then another party member moved the cleric back-and-forth on his turn
The monster was hit with it two times before it even got a turn that round

Needs an errata for ONCE PER ROUND or something about not working with forced movement

"Whenever the Emanation enters a creature's space... the creature must make a Wisdom saving throw"; "A creature makes this save only once per turn."

The wording for these Emanation spells is clunky and confusing. What is it: "whenever" or "once per turn" ? The answer is obviously "Once per turn." They could have found a better way to express this.

Quote from Benz74M >>

"Whenever the Emanation enters a creature's space... the creature must make a Wisdom saving throw"; "A creature makes this save only once per turn."

The wording for these Emanation spells is clunky and confusing. What is it: "whenever" or "once per turn" ? The answer is obviously "Once per turn." They could have found a better way to express this.

Both are correct; they're saying two different things. "Whenever the Emanation enters a creature's space" is telling you that the spell can deal damage to multiple creatures per turn if it enters multiple creatures' spaces. The "once per turn" part is telling you that a specific creature can only be damaged by it once per turn.