Assuming WoW, it actually depends where you're farming

I'm going through the pain of farming motes for another Frozen Shadow Weave set with my (solo) affliction-specced 70 Warlock and it's deeply painful.

"Why is it painful?" I hear you cry (!). Because it's highly competitive and I simply CANNOT compete with Hunters.

Even if I send the pet in and tag them with an instant DoT, by the time I've got an actual damage dealing spell off, they've been re-tagged by the hunter doing massive near-instant damage.

The only way I stand a chance is if I manage to pull with a shadowburn or deathcoil.

My wife has a demo-specced lock and has the exact same problem. Even her pet's charge doesn't do enough to keep it tagged. In fact, looking over her shoulder last night she was getting mobs re-tagged by a hunter AND a MS warrior. It was bad enough that I began to wonder if there's some exploit, but seeing the mob's health tumble answered that one.

So my answer: HUNTER. No competition.

Crazy range + massive damage instants on all targets (no worries about fire / frost / shadow resists) + charging pet = win. You don't even need to be fantastically well equipped.

However.... if you're farming in an area where the spawn is as fast as their death rate then an affliction lock is truely awesome.