I'll have to try switching the archers and warhawks around, that's a good idea.

I don't expect the thrashers to live very long, they have high exertion so they can get a long range move and a strong break on whatever has the highest armor. Usually I try to use 2 or 3 willpower on the move and then 2 or 3 willpower on the break, so that they have one left to bloody flail with the next round if they are still alive. They don't normally survive past two rounds but they manage to take out quite a bit of armor before they go down. Maybe more importantly than the armor breaking, the enemy usually moves around a lot trying to kill them, which takes them out of position and often puts them in range for the warhawks.

What shuts it down is strong defensive builds that stay in position. Think of a raidmaster with shieldbangers on each side of him and three archers in the back. I can run up and do strong armor breaks on the shieldbangers but nobody has to move out of formation to kill me. So then they're still deployed like they were when the game started,even though they lost some armor, but both of my thrashers are dead and we are essentially starting a fight where I'm outnumbered 6 to 4.