Melee multiboxing works great in PvE and to some extent it works in PvP but only if you can consistently stun the intended target. I play 5 ret pallies (well played, not too fun anymore with the judgements of the wise nerf) and they've always got a long duration stun ready on rotation. Rogues work too. You can't really rely on slows unless you have an incredible ping but theoretically you can just jog in front of a running enemy turning around occasionally for a swing while your 4 followers hit him. Latency is really what kills this, however.