thanks for the tips.
The rest of the instance is indeed a joke (besides the two elite robots quite in the beginning, when CC is not set up correctly didn't wipe, but always lost 1/2 my toons. FTL-setup FTW )
I am LVL18 now on my team and will try it again tonight. AOE knock back+ shield sounds good (mental note: need to configure that), and I never moved individually out of the ground attacks. (pressed follow so they more or less moved out of it...)
I also read that the big attack of that boss can be interrupted (just got interrupt abilities on tank and dps