hawkeyefan
Legend
I wouldn't expect it to trivialise every combat. It's particularly effective against low-hp melee combatants. Whether that is "too effective" is a matter of taste.
Yes, this is true, of course.
On another thread discussing some similar issues, @hawkeyefan said "My view is that the mechanics are there to simulate the fiction. They serve the fiction. My fiction does not serve the mechanics." This was elaborated as "I prefer for the fiction to matter more than the mechanics. Like in the example above, I don't care if the game mechanics would allow a group of 5 level 10 PCs to defeat 300 orcs. In such a case, the "reality" of the fictional world we are creating is more important to me than the mechanics, and I would have the PCs fail."
If I dislike the fiction of a 3rd level cleric spell giving OA-style capabilities, vs many low-hp enemies, that are on a par with being guarded by the best knights of the realm, why shouldn't I change the mechanics? Why should I instead have to change my fiction (eg turn my gnolls into archers)?
You don't, you can do whatever you want. But if you're going to discuss what you do, which constitutes testing if large mobs of enemies are effective against a group of PCs, and you remove most of the ranged capability of the enemies, and then draw the conclusion that they are weak opponents....expect some folks to point that out. The fiction is what the DM chooses it to be....the monsters behave how the DM chooses....the terrain is up to the DM....with all this points of influence, I think it's clear that the results of the encounter are largely due to DM choice rather than due to some inherent flaw in the game.
I didn't spell it out because I thought it was a given, but my mistake - the way the aura counts as difficult terrain means that someone charging the Cleric will (probably) not reach him in time to do an attack.
This means the attacker has to endure the damage twice: in the first round when entering the aura, in the second from starting in it. Before even getting the chance to make an attack, I mean. Obviously it's better if this damage doesn't reduce you to tatters.
This means Spirit Guardians make you practically immune to melee attacks from anyone that doesn't have the Hit Dice. This is why I want variants of humanoids with CRs up to at least 5, and why I'm disappointed by the MMs strong focus on CR 1/2 and CR 1 humanoids.
The moving forward bit is to inflict damage on anyone trying to stay at the edge of the aura. In practice it extends the danger zone by at least ten feat (assuming you will want to return to your original position at the end of your turn).
I honestly think you may have been playing Spirit Guardians a bit wrong. My understanding of the spell, both from how I read it and from rulings I've seen online, is that the spell does not damage anyone if the cleric moves and his movement is what places the enemy in the area of effect. It only affects a target when they first enter the area of effect, meaning they move into the aura not the aura moving to them, or when they start their turn there.
So depending on their starting points, many of the gnolls should have been able to reach the cleric before going down. If they started just outside the area of effect, on their turn they could enter and then attempt to save; even if they failed their save, they could still move 15' which would put them adjacent to the cleric after being subject to the spell only once.