I love my escort... lets me get things done quickly. Those patrol missions are a breeze... problem is that people don't know how to survive. I've been in some large battles and have yet to die in battle. The trick is to have an Engineer background so you can beef up your shields. Also my science BO has the science team ability... that gives me 2 great shield recharges. I used to have an engineer BO with emergency power to shields (so i had 3 shield buffs) but i found this to be overkill and opted instead for emergency power to weapons. All i can say is i hope they don't nerf cannon rapid fire lol... that thing is soooo OP.
I love my excort... wait did i say that already?
pass on the engineer background, it makes getting the mk3 abilities extremely hard. You really don't need engineering selection in order to survive.