I tanked this successfully for the first time last Friday evening (29th). The only group composition that worked was one with 2 ranged DPS (1 gunslinger, 1 commando). They stayed together around the solid parts of the floor away from me+droid, and any time one of them was targetted by one of those plasma grenades, they moved -- and healer was able to use AE heals to keep them up from random damage.
Every attempt with a melee DPS failed miserably due to Incinerate damage on the DPS, or a plasma grenade being thrown at them and forcing me to move early.
Quite seriously, this boss is FAR too hostile to melee DPS, unless they are massively overgeared and are at the top of their game. Ranged DPS can do the job with far far less hassle.
Mara/Sent with interrupts (and other melee with interrupts im assuming) works just fine. The tank has to be open to moving the boss. And it helps to walk through the game plane before you activate him if you havent done it before.
we had Jugg tank, myself (mara), merc dps, sorc healer. with me being melee and having to be on the boss, it was easier with the merc and sorc near me. the tank would move him when bubbles went out. i was able to interrupt while the tank was moving him. once the first bubbles went out we moved to the edges of the room to avoid lava.
if you have played any other game, Tank goes in front, melee behind. if you follow this rule, no one but the tank will ever get any accidental incinerates.
The hard part is convincing people who have read how "easy" it is with ranged, to even try it with melee. its not harder, its just different.