I have no idea how you have any basis to say stuff like this for a level 19-21 instance. I was the tank, and there is almost no tank gear I can equip. The healer is a friend who I have been duoing all content with thus far.
The biggest problem seemed to not be the AoE damage, but the people being brought down by about 1000 life to the personal DoT on themselves, causing a need for massive massive heals. The healer was not using any DPS abilities, and the healer is Seer (healer) spec.
I mean maybe the two Sentinels we brought weren't performing appropriate DPS to push him down far enough before the fight dragged on too long but I don't know, because there are no DPS meters. Also, a combat log would have cleared up most of my confusion.
If you are two manning this, one of you get your healer droid out for the last boss. But its a REALLY hard fight if you bring all 4 at this level because no one has a dispell to dump the DoT.