I have an interesting and shocking theory: Alterac Valley is reasonably balanced now, with both Horde and Alliance having the same 50:50 chance to win. It's just a theory, I don't have proof for it. But last night I was playing PvP in AV all evening long, and won about half of the games. Plus, if you look at all sorts of blogs and forums, there are now as many Alliance players claiming that Horde always wins AV and Alliance should boycott AV as there are Horde players claiming that Alliance always wins AV. A balance of whiners, so to say. :) Maybe that is the only sort of balance a battleground can ever achieve, equal number of players on both side complaining how unfair it is.
I think the reason why so many people complain about Alterac Valley is a sense of feeling powerless: There are 80 people on the battleground, each of them taking individual decisions on what to do, where to fight, whether to attack or defend. There is little or no coordination on either side. The outcome is very much a result of chance, based on the sum of those 80 people's decisions. Individual skill, gear, or even strategic insight is of very little use, as the other 39 people on your side simply won't cooperate even if you had the tactical mastermind of a Napoleon. To every strategy, there is a counterstrategy. If Horde decides to defend Galvan with 10 people, that can be a smashing success because Alliance is continually sending small groups there that get crushed. Or it could be a total failure because Alliance rushed right past it, and your 10 people end up doing nothing. Or by some fluke all 40 Alliance players arrive at Galvan at the same time, and just crush Horde there. There is no single best strategy for either side, and even more importantly there is no single best strategy for you as individual player.