I don’t think there is an extreme bias. Alterac Valley and Ashran have imbalances - some pretty big ones, including bugs - that should be resolved. Isle of Conquest and Wintergrasp are balanced (but not without fault); I don’t buy that the Hangar being slightly faster for Alliance to reach is an advantage that causes any losses, and I don’t count them being able to shoot the flag as an advantage either as the same works for Horde but with Quarry.
Alterac Valley
- Stormpike Graveyard is easier to assault than the Frostwolf Graveyard, as Commander Duffy is on extended leave (meaning the Horde has one extra elite 20m+ HP commander guarding their graveyards). This is partially the reason for Horde always assaulting SPGY before the Alliance is anywhere near FWGY, and also why it takes Alliance longer to assault the southern part of the map.
- Iceblood chokepoint
- (Bug) Dun Baldar is not currently mapped, meaning Horde (and Alliance) players can instantly ressurect upon death. This is much more beneficial bug for the assaulting team, as they can buy precious time on recaps. I had a game recently where we had killed the 4 druids and rogues in the bunker with 40 seconds to go, but due to this bug lost the bunker as they all resurrected.
- Vanndar Stormpike does less damage than Drek’Thar (because of Thunderclap vs Whirlwind)
Ashran
- 15% stat flowers, stacking with melee buff, stacking with base defense buffs
- Various Horde NPCs do significantly more damage than their Alliance counterparts
Oddly, despite these imbalances (which while they don’t seem very big by themselves, all add up and that’s before you throw in player morale), you’ll see some Horde players insisting it’s all because of supreme play and the Alliance is just terrible, yet you don’t see the same kind of win discrepancies in normal randoms because those are a lot more equal in terms of balance.