The Dremora in Oblivion didn't look that different from the Dremora in Morrowind...
Well, their armor did, due to the style of the Daedric armor in the game, but for the faces, either one doesn't make that much difference to me. Though I did like how Oblivion's Dremora were NPCs instead of creatures, even though it wasn't really fully taken advantage of. I also liked the idea of having various classes of Dremora instead of just Dremora and Dremora Lords. Though I did kind of like how Morrowind's Dremora could have leveled weapon drops of a variety of different materials, instead of just knockoff Daedric weapons that aren't nearly strong enough to justify their weight and real Daedric weapons for the highest level ones. But I'm speaking mostly of the mechanics for implementation there, for the designs, I'd actually like something new, because I want to see what new things Bethesda can come up with for the Dremora, and besides, the armor on the Dremora looked identicle to Daedric armor in both Morrowind and Oblivion, even though in Morrowind, it was just part of their creature models whereas in Oblivion, they were wearing armor, although only the real Daedric armor that the highest level ones wore could actually be looted. In any case, it would only make sense for them to look like they're wearing Daedric armor in Skyrim too, whether they actually are or it's just part of their models, and since I'm sure Daedric armor will get a new design, of course the Dremora armor should too.
Though as far as how common they are, Morrowind's approach of having them as summons and spawns in some dungeon would be more appropriate for Skyrim, since the Oblivion invasion is over. And yes, Dremora should be in the game. Why would you need to ask if they should or not? They've been a standard creature in the series since well before the Oblivion crisis, so I see no reason why we shouldn't see them after it.
In Oblivion they had ugly, unnatural shaped faces,
So did all the other NPCs in Oblivion.