When a quest giver is killed, all of the rewards from current quest and future quests should be rewarded to the player.
I know this would create exploit nonsenses, but I am thinking for players like myself, because after a while logging in and going from 9 or 10 active quests to just 5 or less, can be bit annoying. Sure jUsT Do oTHeR QuEsT excuse is dumb for those who don't pursue the fun exploration activity like questing.
Also isn't there like max 5 quests per quest giver? Or is it infinite amount, if infinite forget about it, if it's just five and I done first 2, I would like my other 3 be rewarded if some one chopped the tree down and didn't know that it was a quest giver.