Alot of people kill quest givers to fuck with noobs, i think this change would be smart. It will at least stop griefing quest givers in most cases, and won't hurt people who have a claim with a quest giver on it, and want to get rid of it.
The other way to handle it is giving you a new quest giver if your's is killed, however this is a raw deal most of the time, since you might be forced to go farther and farther from where you live.