That could be the case. I'll check it out in training and mess with the timing.
As for getting cr.B instead of db+B, if I'm just trying to poke out of my opponent's pressure with cr.B, don't I need to be holding block? I guess once I'm in blockstun I don't really need to be holding back anymore, but I'm not really good or smart enough to know when I can reasonably expect to successfully land a cr.B, so I'm usually holding down-back the whole time until I can actually confirm a hit.
If you're in a true block string, then you only need to block the first hit.
You can't block something, and poke at the same time. If you're holding db, and pressing a button, then you're attacking, not blocking. If the opponent throws something out that beats your move, then you'll get hit even if you're holding db, because you pressed a button.
If you're going to press a button, then move the stick to down. After you're done pressing your button(s) move it to back or db assuming your attack failed, and you want to block again. This will take some getting used to. I had to learn this technique in the opposite direction. I was used to starting BnB's with EX Kyo from df, but doing that with Kula causes her to slide, so I had to work on running in, and pressing down before pressing my lights.
Again, I'm not sure if starting from down is going to help prevent your super from coming out, but it's worth a shot. I suspect because you're starting from db that you're rolling the stick to forward and hitting d, df along the way thus completing that super when you try to qcb later. If you start from down, then you won't have the down (start of maiden masher) buffered since you were already holding down.