This is a known issue, and it's been stated that HE power has been tweaked for the patch. So, I think the AP will remain about as effective as it is now (one or two bursts usually sufficient to take out a BMP), while the HE effect will be greatly reduced. Seems about right to me.
By the way, my experience with AP rounds against BMP's is quite a bit different from yours. What I've seen is that it usually takes on the order of 5 AP hits to get a fire going. I've never been unable to take one out with AP. Incidentally, I actually took out an Abrams with the 30mm AP the other night in multiplayer. It took about 10 rounds from 500m, firing down directly onto the top turret armor. The Abrams was previously damaged by nearby 80mm rocket impacts, however.