Build need to change with your level (aika online gold) up. Rifleman is one of the worst PvE classes in the 40-50 level range in game. But you can 1-2 hit mobs but only at high relative MP costs and without AoEing.
We know that a good PvP build will double just fine as a PvE build just due to the sheer damage output. Who needs leg shot when 1 hollow point nearly one hits everything? We strongly suggest you just get your sonic blast and incendiary grenade and be nice to clerics, paladins, warlocks, and warriors.
You need to know that Rifleman can not tank in Aika, therefore no way we can take on 2-3mobs on at the same time. Pve- 1shot kill the target is more than enough, because Rifleman focuses on single target.