I've been enjoying flying Deathrain with Jonus. Deathrain paves the way with bombs and Jonus lets both of them be efficient with Barrage Rockets. I could always throw in more Scimitars with Barrage Rockets but they're pretty weak once Jonus dies, so I've been looking at other options. I've tried Whisper plus Duchess as mini-aces and that was okay, but it seems like a Defender could work well:

Rexler Brath + Juke + Homing Missiles + FCS (94)
Deathrain + Barrage Rockets + Trajectory Sim + Proton Bombs + Seismic + Ablative (63)
Jonus + Barrage Rockets (42)

Total: 199

Deathrain and Jonus do solid damage but will definitely go down to heavy firepower, but if I can trade well then I think I'd be happy to have Rexler handling the late game. I could also drop some upgrades (Homing, FCS, Ablative Plating) to make room for Advanced Sensors on Rexler, but I don't know if that's a better idea or not.

Rex is a monster late game. I doubt you'll really need AdvS in this set up, it makes him hard to pin down but you'd exchange that for some of his damage output. I use it on Defenders when they need to weather everything thrown at them.

If you protect him a little early on, and the other 2 put some decent damage in, he should still be healthy enough to just wade in and kill things. He's durable but not so much that you'd want him taking a lot of fire in the 1st exchanges.