I'm not certain what people are trying to achieve with the argument about griefers. If the game is to have PvP combat and skills that affect that combat, then it stands to reason that regardless of what system is implemented, people who work hard and level up their combat skills are going to come out on top. People are going to die no matter what you do.
There's a certain point where that needs to be accepted as part of the game. Potjeh is slightly correct in that the solution to "the GOON problem" (replace GOON with any large group that decides to go on a murderous rampage) is for other groups to combine their efforts and strike back. However, any group with a large player base to draw from is always going to have an advantage over any other group. And so they should.
Organisation in an MMO is crucial. The question boils down to how much of an advantage they should have and how difficult it should be to attack a town. People are in fact relatively safe in that they can simply "log-out" and provided they've not committed any crimes, be safe from summoning. The attackers take a risk in that their kills will leave scents and with the appropriate skills, organisation and ability, they can be taken out even while offline. Something which has happened.
Being able to build massive fortresses, wall in and never come out might be fun but that will need to be balanced with mechanics that allow people to attack those fortress-like towns. Of course, that also means the most-well organised group will have the best fortress and the best attacking capability. The GOONS, as a well-organised group, should for all intents and purposes be quite able to hold the entire world to ransom should they have the people and the ability to pull it off. No system is going to change that.
Yes, some people will get butthurt and rage quit. Others will try and organise a larger group to fight back. Some will sue for peace. Others run off and hope they can stay away from it all. The politics / fall-out and how people choose to respond to that, I see as an integral part of the game.
But epic day long battles - firing arrows from the battlements of castles as the siege engines batter the walls - would be pretty cool.