I'm just not sure that balancing complaints aren't also valid before maxing out the characters. Obviously the upgrades are going to make some people's characters more useful than yours if you don't have them maxed but there should be some balance between characters on the same level. I think people are noticing that when playing their own characters. With level upgrades being so different for each character at each level, it would be a hard task. However, they kinda set themselves up for that when they did upgrades in this way. I guess I'm saying balance belongs at all levels, not just end game.
Edit - personally, I never expected a great deal of balance in this game and I'm not even really advocating all that hard for it. Neither GW game felt particularly "balanced" and I think balance is going to mean hugely different things for different people.
Edit 2 - I wouldn't want to tell someone that is looking for balanced gameplay that they should buy the game, play for 60+ hours and that by then their characters should balance out more. I don't play a ton of PvP so that may be a reasonable amount of time to play before seeing some balance between characters of the same level. I don't really focus on that much myself, I just thought it was reasonable to expect balance throughout a game if that was a goal. I like playing with my kids and we play the characters that we find fun and fit our playstyle, balanced or not. It's also part of the reason private games could be more fun, but that's a whole other thread topic. (Also took out direct @)