Dude, stop trying with the gotcha moments. This isn't one. I used the 5th level example because it was easier to prove the point. A point which you still haven't shown the math on to disprove despite me asking several times.
Here is the math using example your cherry picked example and set up that was changed to 5th level and assuming you don't lose concentration on the casting and assuming initiative is you then the fighter, then the Hobgoblins (best case):
1. You and the fighter cast spirit guardians. Those hobgoblins need a 15 to save and it does 11.4 damage to each on the fighters turn - 22.8 damage on average using 2 actions, a 1st level slot and a 3rd level slot. It does this on the fighters turn, assuming you hold onto the concentration the whole time.
2. You cast a normal "little" spirit guardians alone and the fighter uses multiattack
Your spirit guardians comes up on your turn. On the fighters turn he uses multiattack and tactical shift. Using a relatively weak DPR build, an attack action with a 1d8 weapon, dueling and push (pushing them into your little spirit guardians), you do an average of 24.35 damage. This uses 1 3rd level spell slot and 1 use of second wind.
So with your cherry picked set up and assuming the best possible initiative order, and no concentration checks during the casting the MATH shows you use more resources and do less damage on average than just casting a smaller spirit guardians and attacking.
This isn't a gotcha moment, it is illustrating the shortfalls in play.
If we were talking about 11th level, then the SG would be upcast and doing a lot more than 3d8 damage to each creature
The highest level you can cast Spirit Guardians with a 11 level Cleric is a 5th level casting (assuming saving a slot for Blade Barrier). That is not a lot more damage. It is 9 more damage on a failed save or about 7 more damage on average including saves. That is far short of what an 11th level Eldrtich Knight is going to do with an attack action.
You wouldn't, but lots of people would when they see how clearly it's better for the party.
Execept in most cases it is clearly worse. Cool and neat yes, better no.
I didn't just say so. I said where
it came from. You still haven't shown any evidence that combat rarely takes more than 2 rounds, less for higher level. You were the one to make that claim originally, remember.
I said 3 rounds and that is from this board and this thread:
I know they don't all last the same, but I'm curious if many combats go past round 5.....This isn't for a research paper, just go with your gut.
thanks!
So unless you can actually prove that combat is as short as you claim, and you can show the math where the damage on one round of attacks is more than all of the damage SG does in total (each round and to all opponents), I think I'm done here.
You can't prove that it is as long as you claim, nor that it will last multiple rounds, especially considering concentration.
Again let's use your cherry picked example. Assuming the Cleric has a 20 AC, 18 Wisdom, 14 Constitution and 36hps and assuming you kill 3 Hobgoblins on every single round:
There are only 2 targets for the enemies to attack and with spirit guardians up they are going to concentrate on the cleric. So you have 8 Hobgoblins that are going to attack the Cleric and one Cult Fanatic that is going to cast Hold Person and Spiritual Weapon at the Cleric.
Chance of maintaining concentration through one round (8 Hob attacks, spiritual weapon, hold person): 36%
Chance of maintaining concentration through 2 rounds (5 more Hob attacks, spiritual weapon): 16%
Chance of maintaining concentration through 3 rounds (2 more Hob attacks, spiritual weapon): 10%
The does not include critical hits, pack tactics for the Hobgoblins or any action attacks by the Cult Fanatic against the Cleric.
So most of the time SG does not make it past ONE round using your cherry picked example and it is very rare that it will last 3 rounds!
If you don't like any of the assumptions I made then tell me what assumptions you want me to use. Unless those assumptions are intelligent enemies being stupid you are not going to be holding down SG and damaging enemies for round over round over round for 4-5 rounds or so.