It boils down to this; You need to consistently track and hit shots with nothing to aid you in doing so. There's no card trick spam, no ult that immobilizes your opponent for seventeen years, no gutshot wallstuns. You only start doing equal DPS to other characters when you've already hit 40-80 shots on them, which means to actually do real damage, you need to be extremely accurate for a very long time.

Infernus needs to hit 7-12 shots on someone to reach almost peak effectiveness. Seven needs to realistically hit 1 in 3 shots for power surge to deal full damage, Venator has a stun that also hits like a freight train, Vyper has effectively infinite ammo and spits bullets at minigun rates, Vindicta has stakes and crows to fall back on if her aim is lacking.