yes not sure why you would level like this but you can level with your friends though quests so why slow level grinding oh sorry mean power level ;).
and if you just happen to play on a server with loads off horde/ally killing you makeing it a pain to level on a pvp server.
You could move one char to a low pop pve realm and then use a 2nd battle.net (this is the olny way btw to inv your salf into a group ;) you could ask a realID or battle-Tag friend to make the group they can leave after jsut rember the leader is the server you use ;) ) to make the group on the low pop pve realm then move it back at level 90. saves moving all 5 and then all 5 back;)