So far Burning Legion US has been an awesome server to Multibox on. The MB support is actually quite good here, I never get needlessly ganked by high level alliance, and 99% of horde I see /cheer or tell me how cool it is. I've been playing on BL US since I started playing WoW years ago so I guess I'm just lucky that the community supports multiboxers. I hardly even get BG hate so the battlegroup must also be nice.