Maybe it is just me or is it really REALLY annoying that certain that most Npc's that can vital side quests can be killed but certain Npc's that have side quest can't.

I really wish that all Npc's that give out quest like these couldn't die because then you have to replay the entire game just to do get a chance to do them again because once these specific Npc's die they never respawn.

Hope I don't sound stupid but I lost 3 daedric quests due to dragon's killing off this important characters only not to think its that BIG of a deal and then getting royally screwed over in the long run.

Faendal and Ankor (or something like that, the blacksmith you meet at the beginning) died when I was attacked by some bandits, so Quest-NPCs can die...

I finished their quests though, I think. But Faendal was an archery teacher so he had still some use for me... the found the other teacher really late in the game and the search was quite annoying.