Removal of the medic features from Assault made it a class with no identity or purpose.
Assault Rifles are terrible and there's no reason to use one over a Carbine or SMG. They lack punching power and kick all over the place. Meanwhile most SMGs are just lasers with minimal damage fall off. So its signature weapon is mediocre. Adrenaline is probably the most useless thing I've seen in an FPS. Using the Adrenaline Injector is a trap that just takes 3 seconds of your time for a inane buff. Absolutely useless. The only thing it has going for it is being able to double carry a shotgun.
Maybe give them more ammo and extra grenades or something. I don't know, but they need something because they are just the worst class to pick. Recons get all kinds of map knowledge and spotting. Support has ammo and healing. Engineer can kill armor. Assault... it uh, shoots people I guess.