1) True PvP Server -- what is the point of having troops -- to defend against the barbarians and such -- and if a true PvP server were made these "and such" could be expanded upon and of course gauged to the player's current power level. Further perhaps some of these "and suchs" are things like natural disasters and/or diseases that you have to create a plan for to devise methods of surviving these kind of things.
2) Is this kind of game fun -- yes it is for some but -- but yes not fun for war-mongers because they are all about stomping all over the little guy and rarely take on true challenges. Sure there are a handful of war-mongers that enjoy challenges but more often than not that kind of game just promotes bully-tactics and nothing more. Which has proven, time and time again to ruin a game in the long run. So for those who wish to war-monger they join a server that is dedicated to it and watch it build up and die off, again and again and again. While those who wish to not be subjected to such can go and enjoy the game flavor and such in a world of challenge without needing to worry about the bully-types that get off on making a game less fun for others.
3) Now in my opinion a semi-Peace Server (which has been described) should require an even smaller ratio of say no more than 1.25% of the defenders strength and where tactics beyond over-whelming force are actually required -- takes no brains to attack another player when you are twice as powerful as they are. This would then mean that even if you did attack someone and they used solid defensive tactics and your attacking tactics were just throw troops at them you could easily lose even if you had superior attacking power. This would promote thinkers versus bullies -- which most in my experience in a multitude of games that PvE servers promote to the point that, even though I often beat greater armies I get tired of the brainless folks that can only use overwhelming forces to beat someone. That and many war servers do not reflect all the tactics of war or even none at all. I have encountered an extreme few where you could utilize most of the tactics of war but those were extremely rare and hard for most war-mongers to succeed and since it depends on PvE with brains very few succeeded long term. This is why a mix of balanced-PvE with PvP options would help a game stay around longer but again the PvE has to be balanced as soon as it gets out of whack for whatever reason the bully-types will exploit that and go back to brainless tactics.
I say all that mainly because I am a proponent of PvP having gotten tired of most PvE style games as they lack in the ability to exercise tactical maneuvers and long term strategical thinking that would had been used in real life and simply devolve into the one with the biggest number wins. No morale, no tactical maneuvers, no nothing beyond -- Attacker's (Attack Power / Defense Power) versus the Defender's (Attack Power / Defense Power) <-- not that can integrate more complex math but most war games basically boil down to that unless you can encounter one where the developers actually factored in how to implement all the various tactics that would have been available to a real leader
So -- Is there a True PvP Server -- or is the Peace Server (aka only semi-PvP with some PvE still in place) the only thing that is close to that.