SMR with target finder and select fire is vicious, you guys werent kidding. Then throw in either foregrip or quickdraw handle or laser sight or whatever your flavor is. Been using that with shock bombs and bouncing bettys (scavenger with this almost OP) and I think I have finally turned the tide on the SMG heroes.
For killstreaks Im going UAV, Sentry Gun, and either Hellfire missile or Lightning Strike. Those are low enough to get pretty consistently but also provide good kills. The sentry gun in particular is a freaking beast, its on steroids.
I went from struggling hard to be 14-15 to going 30-13, and Im not that great.