Hmmm... Well, I think perhaps "assassination" et cetera might have been possible for the lesser daedra. Admittedly a little pointless, considering that they get reformed in the Waters of Oblivion.
And people come back through the dreamsleeve apparently, could just be different names for the same thing. There must be more to it than hitting respawn with them.
As for the Aedra... well, they sacrificed themselves to help create the Mundus, so I suppose they care about what their creation is doing. Or, maybe they don't, and their "spheres" of influence are just contrivances of the residents of the Mundus.
That is, the ones that aren't political constructs. But as we saw in Daggerfall, some of the divines are more active than others. Stendarr might save your life if you worship him, but in that game it was a stiffer choice because each temple was a guild.
I figured the Daedra's interest in mortals is sort of like the Demons in the Xanth book series (by Piers Anthony); the Demons like to place bets on how mortals in Xanth or Earth will handle a situation. Why? Because it isn't set in stone, it relieves the boredom that comes with being almost god-like. So, maybe the Daedra Princes are bored and want to see/manipulate what makes these silly mortals tick. Maybe, to them, Mundus is like an RTS game or The Sims or Creatures or something...
Wasn't there something in Battlespire on this? I think it is for some kind of sick enjoyment. or maybe it's just base instinct? Like humans have the base instincts to wake up, eat, go do your thing, procreate take one good crap and go back to bed. Maybe dagon wakes up thinks Wake up, don't eat because he's immortal and dosen't need it (even though he probably could eat but that's a whole nother can o' worms), level a continent, take one good crap and go back to bed?
I don't remember that part of Battlespire if it was there, but Clavicus Vile gave a good speech about it in Redguard. The daedra are powerful immortals who are unfortunately bound by Akatosh to this slow moving linear time scheme. So, if you can have anything or do most anything whenever you want, what is going to happen to you? You do what you enjoy doing best, and even that can get monotonous. A life of tautology can grind you down. That's why people have a midlife crisis after awhile. The way the daedra lords deal with this is having fun with what they can't control, the mortal realm. Daedric princes are gambling junkies looking for the next bet.