What group? Most of my SERVER can't figure this FP out, even after I told them that the healer stays out and the others cover them... explained how turrets work... etc. A LOT of regular non-hardcore players cannot figure out this instance, at all!
Dude, I was in the same position you were. I couldn't figure it out. So what did I do? I looked around for what other people did, and guess what? Turning the turrets inwards so you kill colicoids on the opposite side you started facing, actually did the trick. Now, instead of wondering why you can't beat it at 50, change your tactic!