Depends on what sniper and what mode of pvp you're playing. An ideal sniper (for HoW snipers) is something with higher impact like her benevolence. This allows you to kill enemies once they revive (trials/skirmish/self res warlock) in one shot as well as bladedancers. Ideal rolls depend on the player. I went with hidden hand and shoot to loot. It has been working very well for me. Other than that you want a scope you are comfortable with (I would try an ambush scope or tacsys) and a middle tree that suits your play style (remember that things like armor piercing slow weapon handling).