Assault definitely seems to be the weakest class with 30 rd rifles that take up to 6 shots center-mass to kill. I've only been running Assault on Defense to keep my teammates off the respawn delays, otherwise I'm playing Recon sans sniper scope and strategically placing mobile spawns. Two shots center-mass with a Mk11 will drop guys quick, forget laying prone and counter sniping, you gotta' get in the fight to do your team any good. In the last two stages (escalators and apartments) I'll go Support so I can knock down several guys quickly, you seem to run into a lot more crowds later on. Only use I see for Engineer on this map is using rockets to clear obstructions, but then you really don't need someone doing that full-time.