I feel I need to clarify some misconceptions here.
1) The pvp won't become numerically unbalanced because there are 3 sides in each campaign (instance of a pvp zone) and each side is limited how many people can join a particular campaign (with soft and hard limits, the details of which aren't important). Thus, it will be unlikely for one side to dominate both the other two in numbers alone (though possible imbalance in certain times of day is possible)
2) The ability of it to manage framerate during sieges is actually pretty good. Good programming made it simply adjust the view distance, and I can say that while I do not have a particularly strong PC I had no problems even during crowded sieges. While it may be true that you can see up to 200 at once, if your PC can't handle it, then *you* won't.
3) Whether the combat is good or bad though is up to personal taste however I suspect. And it's worth mentioning that unless you're in alpha you haven't played combat at higher levels, so I think it's premature to dismiss it.