It's not a problem that's cropped up a lot for me, but I can imagine if you wanted to run a dual summoner army style game that it could get annoying.
I don't see why NPCs should be allowed to kill steal, or why kill stealing takes exp away from you.
How many scenarios are there when you can sit by and let NPCs farm while you leech their exp? As opposed to scenarios in which NPCs/Summons KS and take your exp?
