But the fact that the Dragonborn stems from a Daedric prince that's not really that prominent or suitable for being the cause of the Dragonborn is kind of a letdown. The nature of the Dragonborn isn't even well explained. It's just that Miraak got "knowledge" from Hermaeus Mora and that's it. Nothing about anything else we know about the Dragonborns. Nothing about how they have the blood and soul of a dragon, nothing about how they can consume dragons' souls, and nothing about how they have such intuitive use of the Thu'um.
It's even explained that being a Dragonborn is a gift from Akatosh, yet he's never mentioned.
And then Miraak's Staff/Sword/Robes are tied to Hermaeus in that they have tentacle powers. Tentacles =/= dragons. This is DRAGONborn, not "Octoborn" or something. We should be getting stuff with dragon-based powers. Granted this stuff is cool, I feel like Apocrypha, Miraak's equipment, and all this stuff should have been used in a different manner.
I felt that this DLC was too overshadowed by Hermaeus Mora. In Dawnguard, they didn't throw Molag Bal in your face every single quest. They just said that he was the origin of vampires, but it wasn't all centered around him. It was centered around the Dawnguard vs. Volkihar. This DLC should have been centered around Dragonborn vs Dragonborn. We don't even get an explanation for the cultists that Miraak has! They're just there for like two quests and then never seen again.
P.S.: While I was disappointed (mostly, not totally) by the DLC's main questline, I do very much enjoy the rest of it. Solstheim is a very nice expansion, and all the new content is awesome. Except for Dragon Riding, that is absolute garbage.