Yesterday evening I went to some BG's again and this time ally had 1-2 players more everytime. It was a bit boring and I felt bad for the Horde team. Since this is the "suggestions" part of the forum, I have following suggestion:
The BG script should check how many players already joined the battleground and if a player joins into a BG where the number of players in each team are even, the player should be kicked without deserter punishment.