Assault is a totally viable spec. I'm consistently top dps in PvP and have to watch my aggro in PvE quite frequently. It's a lot more mobile than gunnery too. It's a high maintenance spec however requiring a lot of focus. If that's not for you then maybe being a one button spammer is your ticket.
I use a 3/6/32 spec
Combat Medic:
Field Training 3/3
Gunnery:
Havoc Rounds 2/2
Ironsights 3/3
Special Munitions 1/1
Assault Specialist:
Target Lock 3/3
Soldier's Endurance 3/3*
Sweltering Heat 2/2
Superheated Plasma 3/3
High Friction Bolts 2/2
Degauss 2/2
Incendiary Round 1/1
Nightvision Scope 2/2
Ionic Accelerator 3/3
Rain of Fire 3/3
Assault Trooper 2/2
Adrenaline Fueled 2/2
Burnout 3/3
Assault Plastique 1/1
As far as rotation goes I use IR, HiB, FA, HiB (if Proc), AP, If no HiB proc then CB and HS until FA is back up. The rotation isn't perfect sometimes you have to wait on HiB a little by throwing another HS in there or another CB. I also add this into it if the situation allows. Res Powercell, Tech Override, then Plasma Grenade. Most of this is instant cast so you are able to avoid and move around while still dishing out a lot of damage particularly in boss fights in ops where standing still isn't an option most of the time. Hope this helps.