A bit nonplussed that this is a daily; I hope it's just one quest from a large pool, but today is the first day it unlocked on my server happily, it is by no means guaranteed to come up daily.
Died twice to the [npc=69406] so far. Both times to [spell=140427]. The problem is, Acidic Regurgitation is a cone attack and leaves a graphic on the ground as he channels the attack... and neither time was I anywhere near that graphic. The second time, he never even turned, but the attack followed me nonetheless. Either way, it ticks for about 150k and will hit you several times if you stand in it, so if it *is* a bug [and not lag or anything else], then this daily is going to be difficult to solo.
Thankfully as Horde, I have a graveyard very close by. {And if you're Alliance, why are you here? Your quest is thataway :D}
ETA: As I noted above, this daily doesn't show up every day. As of this current edit today is day 5 of Stage 2 on my server, and we've seen this quest twice. There are four hubs available during stage 2, of which only three are chosen; and even if Diremoor is one of today's hubs, there are other quests that can fill this daily's "slot". And, given the information in EnviiThelnsane's post, as the Isle progresses we'll see even more hubs, reducing the chances even further. As NeonKitten mentioned in a reply below, this quest is even harder for melee. Unfortunately, if the quest *is* one of the day's dailies, you have to complete it if you wish to get the final reward bag... which among other things has a [low but non-existent] chance of dropping a [item=94222]. I can't speak for any server but my own, but there still seems to be a great deal of camaraderie on the Isle; hopefully it won't be hard to group up for this particular quest.
On a personal note, I am curious if anyone else is having the same problem I have with this quest, that the breath seems to follow me even when the Devilsaur does not turn in my direction.
ETA²: I was on hiatus for several months, and the first day I went back to the Isle, this was a daily. I nearly cried, since it was late in the week and the Isle was pretty empty. I thought about trying the kiting-to-the-Shado-Pan trick I'd read, but I figured, alright, lemme at least give him one chance first. I didn't see any of the bugs I saw the first ten times I did this daily -- I never took unnecessary damage, so I'm willing to guess now that the damage zone and the visual for said zone actually line up finally! Happy day!