I own Morrowind and my GF doesn't. And I play Warden.
We then tried grouping up for a normal Dungeon run.
First, it says invite acceptet, and then it says grouping failed..
And it keeps doing so whatever we try. and who ever invites.
I really hope this is a but as I see not reason way we can't run normal dungeons together even if she don't own Morrowind?
Hope to gen an answer on this.