Maybe add some dangerous Reaperized humans. I find humans always get the short end of the stick. We have to prove ourselves to the galaxy in 1, nobody still believes us in 2, and now in 3 we are the reaper zombies. Marauders, Brutes, Ravagers, Banshee's, even Cannibals look menacing, and can be dangerous. A husk? Give me a break!
Back on topic, the classes seem fun, and I like the weapons. I had an idea for an oracle sniper rifle too, for the Asari, but I'd also like to have seen an AR from them. Maybe a Salarian SMG with built in omni-spikes or something. I'd like something that can use the xbox's pressure sensitive triggers and buttons, but I'm not sure that would work with the PC crowd... or a PS3.. are those pressure sensitive? I think so...
Also, drop cloak, please. It took long enough for sentinels to not all be burdened with Tech Armor, can we please add some flavor to the game again? Garrus never had cloak and he's been a Turian Infiltrator from the get go. Make a damping power like ME1 that slows enemies and their fire rates. It could disable special abilities too (cloaking, summoning drones, banshee-porting). At level six one upgrade can reduce the time, but stop a target from being able to do insta-kills!
Also, I'd switch around some of those classes. There already is a Batarian Sentinel, an Asari Vanguard, a Vorcha Soldier, and a Salarian Engineer. What about an Asari Sentinel, a Batarian Engineer, a Vorcha Vanguard and and a Salarian Soldier?