Well assuming someone couldnt kill you in a global, do you really want to play arena matches that last 30 minutes long? Problem comes in when a healer gets to sit down and drink. You literally have to keep an eye on everyone since you are trying too oom the healers and stay away from the dps (while trying to kill them too.) Sounds like a lot to do =)

Although Im sure someone will post saying thats what all MBers do =P