Actually, all the bats and rats can come as adds for me at 55. It does seem that I can stand without the rats aggroing while fighting bats, but if I sit while fighting a bat they'll come running.
Epic pet can solo any of the bats and rats in the cave: it's actually not bad AA XP at 55 even though they often spawn as light blue, and quite a bit of cash to be made from augments and vendor loot.