Would a story set after the Dragonborn dlc story line break anything lore wise? If it doesn't  include the Dragonborn protagonist? 

I was wondering, can a dremora or other daedra breed with humans or elves?

So terribly sorry that one of us has not gotten back to you. The holidays happen and sometimes posts are missed. I think you can totally set a story after the events of the Dragonborn dlc and not break anything, so long as you respect what has happened. If you're curious to see how this is accomplished well, check out Exuro's blog, A Dance with Daedra. While it does feature the Dragonborn in it, the focus is on another character entirely. I frankly don't see any reason why you can't have a story that doesn't feature the dragonborn, though, you many consider mentioning him or her in passing, just so people understand where you're coming from. I didn't play Oblivion, yet I mention the Champion of Cyrodiil and her contribution to my world in my blog, Straag Rod. Others use elements from the previous games too. Have a read of the blogs here. We get pretty creative. 

I don't think what you're doing is lore-breaking. 

In a word; no. Considering that not even Kahjiit nor Argonians can, and they live in the same realm, it is certain that Daedric creatures, though humanoid, cannot either.

Oh, I see. I was planning on making a half daedra, half human character. 

Anyway, thanks. Guess I have to come up with another strange character.

It might be possible to combine deadra creatia with a mortal soul through a ritual or a gift from a Prince to create a half-breed. I don't know of any lore to back this up though.

Is it lore breaking to be a dremora in Tamriel? and either being dragonborn as a dremora?

And by this I mean like left behind after the Oblivion Crisis or a 'unbound' dremora that was summoned and stayed instead of returning to Oblivion