I just watched a Dawnstar guard get killed fighting some imperial soldiers. I didn't involve myself, but now i feel like i should have reloaded so the event could be avoided.

Can i feel better in knowing that guards respawn? That they are more a clone army than real NPCs?

Yes, they respawn. I suffered a glitch in Whiterun where I was attacked by the entire guardforce for no reason. They came back as the cell reset. (3 days, I believe. This is how it was in past Elder Scrolls games.)

Either they do or Markarth has a couple thousand reservists.

Anything with a generic name and not a unique name (like "Whiterun Guard" instead of "Roary Finkelstein") respawns.

Thanks everyone.

Feel heaps better:)

The Jarl of Winterhold?

Yes, they do respawn, complete with pre-arrowed knees for your convenience.