Despite a pretty good effort by the Alliance, though, we failed to win. At the high point, we managed to control 2 buildings, and were contesting a third, but we weren't able to pull it out.
Simply put, taking Tol Barad is just too hard. Defenders don't even need to take a hold a building - so long as they can deny one point, they can keep control. All other things being equal, in a 30-man battle, the attackers are always going to be facing a superior defensive force, because the defenders can - without risk - abandon one or even two points of defense, and mass at the third. In WoW, as in real life, defending a point already has advantages over attacking. Tol Barad's win criteria just magnifies this difference.
There's been any number of articles and blog posts written about the balance problems in Tol Barad. From my point of view, there's two real problems: the difficulty of gaining control, and the lack of incentives to gain control.
Let's look at the last one first. Lack of incentives? Why, yes. In Wrath, the big PvP area was Wintergrasp. Gaining control of Wintergrasp meant that you got access to daily (then weekly) quests in the zone. On top of that, you could collect Stone Keeper's Shards from dungeon bosses. It also meant that you got access to a special raid instance with high-end loot. Everyone - meaning both PvP and PvE players - benefited from their faction taking and holding Wintergrasp.
Compare and contrast with Tol Barad, where the winning side gets... access to a half-dozen daily quests, which reward Tol Barad Commendations.
Which you can get, just as easily (if at a slower rate) by doing the non-PvP related daily quests on the island.
Why, as a casual PvP player, I should beat my head against the wall of Tol Barad?
I still have to give Blizzard kudos for trying to make Tol Barad interesting to the casual PvP and PvE player. Aeth has her eye on the Stump of Time - dripping huge gobs of hit rating, this is obviously PvE gear, obtainable through doing PvP content. I haven't looked, but I wouldn't be surprised to find that there's PvP gear that's primarily obtainable through PvE content as well. After all, that's how Aeth got into PvP in the first place - she won a set of PvP legs from Torvalon in Wintergrasp.
I don't have to participate in the Tol Barad battle to get it, though. Nor does my faction even need to control Tol Barad. Those things are nice, and would make getting my new shiny happen faster, but they're not essential. Consider how many people in Wrath were interested in Wintergrasp... asking who controlled it, when the battle was starting, forming up raids as the start time approached. Now consider how much effort and involvement you've seen for Tol Barad battles in Cataclysm. Really, nobody cares, because there's no reason to care.
So there's no real incentive there. For the amount of effort required, the reward just isn't there... at least for me, and other casual PvP players. If I just want the thrill of PvP, there are any number of other battlegrounds where I can get that, and still have more than a ghost of a chance of being on the winning side.
So, option one: Blizzard can up the incentives, making winning Tol Barad as it exists today much more attractive to each faction. Which brings us to option two: decrease the difficulty of winning Tol Barad to bring it into line with the current incentives.
I really don't have a problem with defending being easier than attacking - as I mentioned, that's the way things are. The problem is that the victory conditions for attacking side aren't just slightly more difficult than the victory conditions for the defending side, they're much more difficult. So Blizzard can either change the victory conditions, or make obtaining the current set of victory conditions less onerous than they currently are.
Some options for changing victory conditions. Reduce the number of buildings the attackers must capture to 2 instead of 3. Or require that the defenders actually defend all the buildings in order to keep control of the zone. If the attackers control all three buildings at the end of the battle, they gain control; if the defenders control all three buildings at the end of the battle, they retain control; otherwise, the zone is contested... and instead of the current crop of daily quests, players get a different set of PvP related dailies.
If we keep the current victory conditions - attackers must take and hold all three buildings - then we can still level the playing field a little bit by giving the attacking players some NPC help. Consider adding the following mechanic: if the attacking players are able to capture two buildings during the battle, then they gain the ability to "raise the vengeful dead". An artifact appears somewhere between the two buildings that requires 3 attacking players to do a 15-second channel. If they can manage to pull off the cast, one of the buildings they control is garrisoned by the vengeful dead: 20 elites friendly to the attacking forces, hostile to the defenders. This gives the attacking side a non-trivial bit of assistance, but only if they're able to (a) capture two buildings, (b) keep those two buildings, and (c) keep the defenders from interrupting a long-running channeling effort that takes away 3 players from their forces.
Something like this would force the defending forces to defend. If they hunker down in one spot and keep control of a single building, then the attacking force will win, period. Instead of being passive defenders, waiting for the attackers to come to them, they would have to make an effort to disrupt the attacker's forces.
Take it all with a grain of salt - I'm a casual PvP player at best, after all, and I'm sure that there's a hundred problems with changing incentives or changing victory conditions that smarter folks than I can point out. Even as it stands right now, Tol Barad is a fun battleground to play in. Long term, though, part of the fun of playing is winning once in a while. Taking that element of fun out of Tol Barad makes it an interesting diversion, and keeps it from becoming a core part of Cataclysm game play.