I suggest doing the citadel dailies for a while if you haven't. It might help a bit because running all five on vehicles pretty much sucks IMO. You get more used to it after doing those dailies. That's where I learned not to press "charge" for example =).

The hardest part is keeping them trampled IMO. I didn't even know I had to do this at first.

Also, I read this instance has been very buggy (e.g., invulnerable champions). Not sure if that is still the case or not.