You're right, our chokepoint is brutal. On my hunter, I stand on the wall and rain down death and destruction as allies try to run up the ramp, and I've seen a few mages slaughter an entire alliance raid on that ramp. However, the narrowness of the chokepoint is balanced out by the fact that it is very short, and the allies can gather safely in the tower at the base of the ramp and prepare for a charge.
As a horde attacking the allies, you've got to try to coax the raid into pushing across that long bridge where you're getting shot by the right tower the entire time. People tend to stop in the middle and engage in long range battles with the allies standing at the end of the bridge. This, of course, accomplishes nothing since both sides rezz right there. Getting people to cross the bridge and assault the bunker is, by far, the hardest part of AV for horde side. It takes at least an hour almost every time. These difficulties are made up for by the fact that we can jump into the back of the right bunker and bypass the lower level guards.
I think it's pretty even.
Oh, and there is a way into the horde base besides the gate. There are a few mounds of snow near the fence that are big enough that you can jump straight over the wall if you're on your mount. You can also get on the ledge around the upper area and enter by the waterfall at the back of our base, and you come in right by our aid station.
I think I'm going to get my gnome warrior on icecrown to 51 and do a few AV's from the alliance side. He's only a few levels away.
I skimmed through this and the even longer rant. But since Jinheim is right more than I am I am inclined to agree. AV chokepoints are balanced. Ever done an 8 hour alliance base bridge camp? They aren't fun.