Early Levels:
Use Deadly Barrage and Armor Piercing shot almost exclusively. About 14 or 15 in each of those. Nice synergy and lets you mow down packs. Armor Piercing is what you can use on terminal bosses. It's tough without Vengeance but good to lower their resistance and follow up with some Impact Shot before a dodge.
Use Impact Shot as your basic attack. Got 5 in the passives and 5 in Driven by Vengeance. 1 in Roll, Lunge, Flashbang, Punish the guilty. I think 2 or 3 in Show no Mercy just because it looks cool. You can swap to flechette at 30, but consider the knockback of Impact shot
Later Levels:
Use all of three skills. Rifle shot for maximum single target dps, Flashbang for any large groups for LONG stuns to rifle shot them down, and escape roll for dodging anything I dont want to touch me. I found Deadly Barrage to be too weak to rely on so in the rare case there are too many mobs for me to mow down with rifle shot i just throw out a flash bang and clear the room before the stun wears off. Plus deadly barrage is a cone where flashbang is a radius attack so you'll usually get more bang for your buck there. The one case where I do use deadly barrage is in survival and group challenges because i have more time to dps the mobs since i am at the back of the line and they usually group well. Focus on some attack speed and stacking as much rifle shot bonuses on gear as possible. Don't forget to grab points into shotgun and impact shot just for the synergy increase.
