I've seen this happen numerous times whilst in combat, normally horde players, who come to Stormwind or whatever, and can infinitely teleport in and out of a dungeon and just not die due to this. It's really frustrating and annoying to deal with, as players can do this whilst in combat, heal themselves up, and reteleport out. I'd request that you maybe prohibit players teleporting in a dungeon when they're in combat.
