My general suggestion would be to say that mandatory character death should be abolished, and players have to mutually agree that death is an option before the RP starts. Official faction events should also not be mandatory death PvP, so more people will join in war events. There will still be salt if someone goes in and gambles their character on a duel with someone, thinking they'll win, and loses, but at the very least people can then participate in official PvP and fight rival factions without having someone come in and merc them because they like player-killing. Without there being a reward for PK seeking (that is, you eliminate people who could potentially become the same strength or rank as you, making your RPs "easier"), you wouldn't really need a hard OOC measure of character strength, you could just go by their rank or training because going into an unwinnable fight and losing to a high-level sith doesn't necessarily mean death. I used to be in a fantasy RP community that had a similar problem, and removing the idea of a "character death warning" and letting people choose if they wanted to escape, get captured, or get killed in fights for plot content made everything better, even though (or partially because) a handful of serial PKers left as a result.