Couple ways
1- Mook Asploder. Acolyte Pistol for Shields/Barriers, then Pull -> Reave. Switch to a Piercing SMG for bosses. Pair with biotic teammates and spam Reave while they spam Dark Channel or Warp or whatever.
2- Radius Warp Bubble. You can Reave -> Bubble -> Reave for combos against all defense types, even armor. It is a high risk high reward playstyle.
I like to do a combination of these two. I use the Acolyte in combination with a Hurricane, BPP, or CSMG, with Warp Ammo, specced either 6/6/6/4/4 or 6/6/4/6/4. Mostly, I go around Acolyte/Pull/Reave-ing all the mooks and let PUGs focus on the bosses. This tends to work pretty well, as PUGs generally like to focus on bosses anyway and get killed by the mooks. I'm saving them from their fate. For bosses, I try to use a combination of Warp Bubble debuff, Reave DOT, Reave/Bubble explosions, and SMG fire to take them down.
Warp Ammo is essential for this build against any enemy except Geth. Even against Geth, I still think it's the best, but I could see using Disruptor against them. Works best against Cerberus, because the Acolyte trivializes Phantoms, and Atlases are easy to keep in the Bubble. Dragoons are a challenge if you can't switch to your SMG fast enough. I just Reave them at a distance, shoot them (with Warp ammo bonus), then dodge them if they get close and drop a bubble on their head for a BE.