Thats sort of the point, the Daedra are god-like beings who have manipulated even the most poerful of mortals for thousands of years, there is no other way becuase the Daedric princes deemed it so.
Gonna have to agree with this.
While the Dragonborn main quest was its own story pretty much, a continuation Herrmy's Daedric quest from the main quest imo. When you first step into Apoc., Hermy even says as much if you got the book in vanilla Skyrim.
The Daedra(even the few good ones) always seemed petty to me. Kinda like deep down they wish they had helped in the creation of Nirn and they mess with the mortals as a way of compensation for that missed opportunity. Its just the way they are(and always have been in TES) and i kinda put my own morality aside with dealing with them, to just get stuff done fast. At least i like Hermy a bit more than some of the other 'Bad' Princes.