Depending on how bad the XI7s get, you need to invest more points in engineering. Not to repair your ship, but to do the 1-point shield moving to bring your shields to the damage, not the other way around. Against an Ackbar wall of fire list like 2AF + MC80 ackbar like to bring that's the first strategy I'd like to try.
There may be no superior defense strategy other than this, other than dodging enemy fire and getting into their un-optimal arcs (by racing ahead of a conga line or trying to get behind them). Since I like running VSD-ISD lists my head is chewing on ideas to try countering it in a shoot-out.
I learned, in my game with doobleg, that that seems to be optimal way for imps to play.
Against rebels, Drive your Flag-SD (ISD or VSD) at them fast and use your picket ships to basiaclly ram their front while your cruiser smashing into their flank.
Against imperials, Drive your Flag-SD in a joust and outflank with your pickets.
Of course that's ultra-general; and Armada is nothing if not the most "specific-situations-trump-all-tactics" game i've ever seen.