When you are at the last boss in a dungeon, login to your rezzer (priest, pally, shaman, or druid) and run him/her to a safe spot by the boss. Log back to the toon you are playing. If you happen to wipe, log back to the rezzer and rez the team. I have used this trick many times in UBRS by leaving my pally at a safe spot and logout. If we have a wipe, I log to the pally to rez the team.
While in the party I tell the group leader to uninvite my rogue and then I log to my pally and run her to a safe spot by the boss and then logout. I log back to my rogue and get invited again by the leader. This way the pally is in a safe area to rez the team in case you wipe. The pally is logged out during the fight so when I log back in, he's alive to rez the fallen members of the team. Just remember that UBRS has a max of 10 man so you can have only 10 in the instance at a time, so when I switch back and forth between the rogue and pally, there's still only 10 man in the instance. I hope this helps.