Honestly with the way this game works, 700-800 is about perfect, not too much that it causes server issues and just enough for multiple zones of relatively smooth RvR action.
Unfortunately it falls off really bad anytime other than the few hours for EU prime time. The NA population for this game is incredibly small because NA really doesnt care about Warhammer anymore they are obsessed with WoW, like id wager at max 10% are NA or something, it really shows during NA evening.
So if you could always make the hours of EU prime time where it is perfect pop I would say absolutely worth playing, but if you are like me and usually only get to play during NA evenings/EU off peak then its prob not worth it right now.