It's funny, i remember the gameplay improving throughout the alpha's and suddenly this map plays really in favour for RED past the first control point. Also, what happened to A at the bridge? Wasn't this 3cp?
BLU spend too much time just trying to clear out the building after CP1. IE 7 minutes just to clear the sentries on the other side of the door, and ledges, then 3 minutes are all that's left to assault the even more SG friendly last point.
It was suicide to attack the last point head on without an uber and almost always better to assault from the structure on the side where demos and soldiers could out range defensive positions on the opposite flank and ambush the rest below/above them from behind where it was fairly easy to kill the engi and make sure your support follows through on the buildings (because you'll probably die in the process when they realise what's happening as you're pretty exposed).
As long as RED don't realise the weakness on their flank, which they'll assume to be the case because it was their old spawn exit, attacks on the point from here were semi effective and we (as defenders) had to replace a number of our sentry guns because of such sneaky demomen; but ultimately they were nothing more than scratches on the surface of our defence despite a 20 second respawn. Afterwards this surprise flanking attack from the old spawn exit was rendered moot just by doing a couple patrols with the other engi's one by one and looking after friendly gear as necassery.
I can't remember what sort of spawn wave advantage BLU get after capping CP1 but it's not nearly enough. You could start by making the smaller entrance into the structure by CP1 one way for BLU so RED can only counter attack through the large door on ground level. This will at least stop RED immediately flanking all the supporting engineer gear where a single soldier or demo could take out 3 players worth of buildings with little to no effort or risk on their part.