PK should always be something you can do, that comes with a risk of punishment. That way killing someone 10 levels lower than you isn't worth the risk. Give people a reason not to bash the noobs, but let people of equal level still fight it out, with some form of punishment coming to the person who attacks first. They'll still do it, but at least from then on it becomes a choice. They have to decide "Is killing this person worth it?" Instead of "Oh a person. Since there is no risk, let's just try nuke them".
PK has always had a chance of losing luck on your weapon (Not sure about this server). Some issues here are that it's very easy to get luck 7 on this server and someone could also change to a PK weapon to avoid cursing the luck 7 weapon. So what can we do? What about a penalty that applies luck -3 to the character that commits the PK for a certain amount of time. If they PK again before that time runs out, it could stack so luck -6. Also, the luck should go into the negatives so if a character has luck 9, and they kill 7 or more ppl they would now have luck -9 which should hit the lowest each hit (opposite of luck + 9).
Another issue I see: (Just gonna use warriors as an example)
The characters have always had the same amount of HP but warriors back in the day or early euro (when mir was great imo) would struggle to get 80 DC. I also believe that Flaming Sword was the most powerful skill. BUT, now there are very powerful skills and kits that are just ridiculously high DC (200 + then if you add BUFFS maybe 300 DC) but the HP is almost the same. Sure there are better pots, and dark armours etc but it doesn't even come close to the damage these characters can do.
I don't play anymore but not because of anything to do with the server. This has been my favorite mir server in a long time.
Best,
/ACANA