Allright, didn't know that. Thought for a moment that Battle Fury worked for ranged too.
Well, no AoE farm means all Sniper needs is a good babysitter. Chen in nearby jungle, Vengeful Spirit, etc.
Sniper has all the tools to be a good carry, he just needs proper enviroment and team to create it.
Edited:
Free Cleave, AoE stun, 180% Damage Ultimate.
There is some carry potential, but the problem is he needs to gank so that his stun is in constant use and in order for Cleave to farm well he needs items. I guess teams just don't feel like letting him carry.
I honestly think that BKB + Daed on Sven is scarier than the same stuff on, I don't know, Drow Ranger ?
Maybe I haven't really seen a carry sven's DPS potential but with drows attack speed + the 300-400 damage she dishes out at max level can probably shoot 2 or 3 arrows compared to 1 hit by sven.