I've seen and blown up all three new mechs, but I'm running a bunch of mods, so actual usable new chassis come slowly. The Crab in particular was a highly unpleasant opponent, with all the lasers it has. Hatchetman has the center torso ammo bomb and is slow, so it dies pretty quickly when you encounter it as long as you focus it down.
From the mods, I do have a couple of Phoenix Hawks (and lost a Warhammer recently).