I've had two characters try to complete the Toothmaul Gully boss achievement. Both had the same problem with the achievement not getting checked off. I submitted a help ticket the first time (I killed Nitch but the bullet point for him wasn't checked off). My ticket was escalated and the CS told me that she could tell I had completed the objective and that I should have gotten credit. After the couple of CS suggestions didn't help (reloading my UI and repairing my client), the only thing she could tell me was to go kill Nitch again. I thought this was reasonable, but it's proving to be trickier than anticipated. The four times I went back to check, I never managed to find him or any other bosses spawning,and there were no boss corpses lying around at any of the spawn points, indicating that none of them had been killed recently. Does the dungeon purposefully have boss dry spells?
I tried the same dungeon achievement with another character. The bosses were spawning, but I only got credit if I (and not the person I grouped with) got the last hit. It's very frustrating to find the boss, get him nearly dead, and then be robbed of the achievement by a passing player who gets the last hit. In other dungeons, anyone who hits the boss gets credit when the boss dies. But I can see how it might be intentional to make the achievement difficult to get.
However, my group member was getting credit for the bosses we killed when he got the last hit, but I was not getting credit even though I was doing more DPS. I personally had to get the last hit to receive credit even though we were grouped together. We're having to hunt down every boss at least twice (once for me and once for him and that is only if there are no other players around) and try to beat all the other players to the last hit. I'm pretty sure this non-group-friendly issue is not purposeful.
Does anyone else have this issue? Is this achievement working as intended?