Re:
I Attack the Darkness achievement.
I teamed up with another person yesterday. She tanked the boss while I looked for the 3 invisible creatures.
Warlock sounded the best for grabbing the creatures, so that's what I used initially, but for some reason the Eye of Kilrogg is bugged more often than not. After casting, the eye just refused to move more than a yard, it always teleports back to zero position. My friend's warlock's Eye also behaved the same, and what's weird is that it only behaves like this in raid (tested in Cenarius' island, and Xavius's fight area) but outside the raid it behaves normally.
Ultimately I switched to DH, and it took quite a few tries to get the achievement since DH's Spectral Sight has a 30 sec CD and much shorter uptime. Here's some tips:
1. After spawning, the creatures will run around the perimeter of the entire area. Getting quick tags on them once spotted is crucial, given the short uptime on Spectral Sight plus there's some RNG involved for the risk of it getting cancelled on taking damage when the boss occasionally targets you. So use a target macro bound with Torment for instant tag.
2. The creatures seem to have fixed spawn locations, so positioning yourself there at exactly the right time will greatly increase the chance of spotting them in that short Sight window. Otherwise, the creatures would have run off somewhere and you'll spend many unsuccessful attempts randomly guessing where they ran off to (easier to just die & reset the encounter). I found success with
this diagram as to the location of the spawn locations. 1st creature at start of pull, 2nd creature at boss 60% hp, and final creature at 30%.
3. At level 20, the creatures have 120k hp. My tanking partner is an 80 toon, so she made quick work of the creatures once I pulled them into the light, but I suppose 2 level 20s can kill them without taking too much time, but definitely one has to be a Monk to quickly dispose the boss at the end once all 3 creatures are down.