This usually isn't a problem for me. In my bg, queue wait time is less than 1 min so I wait and manually join the bg right away with just one char to speed the load time. I usually get in first then I enter my other shamans and move them to a group not filled in (cause I can't move ungrouped player out). A mod that automatically joins a bg would help but I don't know of any. Just dl it to one of your char preferably the nonleader of your group so you can requeue if you want.