Destroying Raiders is key for any DE match up.
Ive played a few mirrors now, and somehow managed to win them. The largest Tech piece that my list brings is 13 Liquifiers (this is a HIGHLY competitive environment, its OK). Those things are GREAT at swatting down Raiders or Voidraven Bombers. Wracks are also a hard unit to efficiently get rid of. T5, 5++/5+++ is just brutal for wyches/incubi to cut thru.
I dont personally use Trueborn, but they are also really good in the mirror because they dont care about -1 to hit.
The main thing about the mirror match is pacing your game. You know how quick the enemy is, and they know how quick you are. Ideally you get to go second, so they can "spring the trap" first. If you go first, and NEED to take those mid points, dont throw your whole army up. Just put a boat with 5 troops onto the edge. Hopefully the opponent springs their trap on that, then you trap their trap. And they dont have enough to trap your trap of their trap (etc).
Its actually a really fun match, makes you a better DE player.