Pvp just accentuates the issue, pve (probably) isn't gonig to be fun for you if you aren't using the keyboard extensively, even on your main. Multiboxing is all about reducing seek time, so people use smaller keyboards, short-hand keyboards, and hardware or software multiplexors with zero seek. You'll still want to place your mice well, though; I've got powers I don't want bound as they aren't in frequent use. Even in pvp I imagine that matters.

On the other hand, it's whatever you like.