IMO mainly sniping was getting frustrated as almost every enemy in the game seems to like to get in your face forcing me to withdraw the sniper so I would go cunning tree if you dont want to melee --- When faced with two choices simply flip a coin. It works because in that brief moment when the coin is in the air. You suddenly know what your hoping for.
Use something like the first build. I suggest: http://talent.87bazillion.com/2/assassin.php?505001500050503055510000000000\ Use scoped revolvers for softening up things, then use repeaters for the rest.