A month of say 80% W for one faction wouldn't be representative, it would be just a blip or anomaly. If that were the common W/L ratio over a longer time then yes, but then Blizz would likely do something to correct the imbalance like racial nerfs/buffs.
Unrated Battleground Win Ratios for Region EU
That doesn't include stats for EotS because of the bug. So overall it's 53/47 Horde favor, a far cry from 80/20. If out of 100 matches you're winning 47 on Alli it's nothing to whine about.
http://www.wow-stats.info/bgwr01.html
Inbred mongo = Dramatized & OJPimpson. kek
/1-finger salute