Due to some debate on this matter I've been pondering the case of team balance for a good while now and decided some months ago to take map end screenshots for every battle I was in or spectated. This has now grown to 269 battles on EU1.
For easy reference I've collected this in a photobucket
SLIDESHOW.
Feel free to post your own. As you can see this is not a place for e-peenery, so go wank off somewhere else if you must.
This is of course not a very scientific approach, but in the least it gives a perspective.
Looking through the screenshots I see a pretty even win/loss ratio, not the 'constant rolling x5 for clan members', as some seem to conjure up. I see a good deal of 4-1 and 4-0's though, especally before the new Master of The Field changes. But this has always been a part of Native and melee-based WB mods, balance often shifts to one side from pretty early on (not unlike many historical battles btw. where the 'rout' was half the battle). But then many again are 4-3, 4-2 maps, if you look.
I also see a bit of banner stacking but not really enough to judge public play as constant pub stomps, at all.
The occasional pub stomp do still happen of course, and while I remember my slight irritation years ago being on the receiving end I honestly don't mind losing anymore, it is part of the game and I guess I've just grown used to it going both ways. My interest in this game is in every single encounter, not the multiplier, which is not an altogether perfect system either way I think anyone will agree. Though constant losing is pretty annoying to anyone, certainly, especially if one's team keeps splitting up for no reason whatsoever.
At least looking at these pictures as a whole leaves the impression that the auto balance works pretty well, or at least decently. If one's team has won 3 rounds it is pretty often you are team switched or your team will lose, the balancer forcing one team to play with a handicap. But this also happens naturally, I remember this from native clan battles too, the winning team gets cocky and coordination suffers, or the losing team gets their act together.