David Bowers wrote an excellent, thoroughly analyzed article about the map imbalance in Alterac Valley. His point is relatively simple: under the new Reinforcement mechanics, the map favors the Horde. He posits that, should the Horde play their best game, the Alliance will not be able to win in Alterac Valley. In fact, according to reports, Alliance in some Battlegroups have boycotted AV altogether. When I first read David's article -- a great read I highly recommend to anyone, by the way -- my initial response was a slight befuddlement. You see, in my Battlegroup, the Alliance win their fair share of Alterac Valley.
In fact, if we go over to Warcraft Realms, we'll see that the Alliance win quite a good number of AV games, too. Furthermore, in some Battlegroups, they completely dominate Alterac Valley. Maybe the Horde of those Battlegroups should read David's article. In it, David outlines how the new Reinforcement mechanic favors the Horde because the map design allows Horde players to reach Stonehearth Bunker, a key objective that awards +63 Honor when burned and eliminates 75 Reinforcements, before the Alliance can reach Iceblood Tower. The new Reinforcement mechanic also makes Iceblood Graveyard a critical defensive bastion that, if defended fully, supposedly prevents the Alliance from getting any Honor from Alterac Valley.