It would be totally ok if they try like 2 times to join the attackers in the first round and then just deal with being in the "wrong" team or go spec. But some of them are trying until the last freakin minute to join the winner-team and that just fucks up the balance even more, because they don't kill anything and the defence doesn't get more players that would do so.
But, to be honest, it's just way too easy to get into the "right" team and i do so, too. Usually one click on the 2nd team is enough to join the attackers. But if not, i can deal with it >:O
Solution (Like mentioned many times before): Let us only choose 1 team, so we join one of the teams randomly.