Yeah you can kill him with single group. you have a monk go up to his room, have a druid on the main floor by the steps heal the monk, chaliak gets agro on the druid, warps downstairs, tank him in the cubby on the sides of the steps between the crystals, rest of the group in the cubby to the left in the crystals. Fight takes like 20 to 30 min but the less people you use the easier he is. Kinda odd like that.
Downed this guy with 9 people the other night on Saryrn. 2 shamans, 1 cleric with necro pumping, Warrior, 2 rogues, SK, chanter. Dropped the ring for us
He needs a good raid force. My guild has just broken into time so is fairly well equipped and it takes us 50+ ppl to kill (we gank feratha also) you need to have casters behind the crystal as said already. Its relatively straight forward if casters are protected - can do with less but takes longer - and the longer it takes the more chance of wipe. Also instead of killing the mob by crystal, get him down to 9ish% hp then snare and he stays in place - you can then re-snare as needed and dont have to worry about re-pops or adds.
Basically this mob is a good old traditional ToV raid one, its all about placement to protect the casters. His ae's basically are cured by pureblood for the poison and lil bit of rc here and there does the job for the fire dot. Other than that u better have a few cc'ers cause of repops usually at the place u fight him.
Common on a level 85 mob in a zone that is min lvl 69 to get to. I would say common is fair for this. Deserve something for killing the chimera packleader.