Nothing does well in a ball like tanks do. MB is basically a ball as you'll never truly master positioning on more than 2 characters. Dual boxing though I've done at the highest levels of raiding in the past. Also did pretty good in 2s. It's hard but doable.

WoW is basically disco fever. You have to dance to win. Learning is one thing and being clever about moving a 5 man team is another. Most MB just run tanks to avoid the dance. The dance matters in PvP, too. Stand in too much bad and it doesn't matter how big your ball is. For wPvP probably best to run 3 healers in a 10 man team and 2 healers in a 5. Just because balls will take enormous damage under the usual circumstances of a counter.