Yep, that is my very favorite TNG ep ever (and I don't generally like time travel) but that is what it was - an alternate, rather than mirror, universe - the Enterprise C survived (squeaking through the rift created by the battle she was in) to transform the TNG universe itself and met up with Enterprise D, which was then a battleship.
There was a mirrored Riker, at least, but I forget the details and they lifted that from the split-Kirk TOS ep, IIRC. Like paranoid_marvin, I'm thinking there was one, too, though. Nothing as elaborate as DS9s great one, but something. Been a long time since I've seen any TNG though.