Are you sure you were in Cleric Stance OP? O.o
Granted, I am SCH, so I don't have DPS problems when I put on all my DoTs, but this quest felt EXTREMELY easy in the HQ i115 gear you get from MSQ (and normal i115 for the missing ones). Just make sure to ALWAYS focus the healer first.

I have not really played AST, and don't know their DPS, but I can't really imagine having problems with this particular one.