It does catch people off guard, which is why it's tempting to do. If you can pay to keep it safe, then that is something as long as you have meter and are willing to spend your attack bar on it. Looks like you get a lot of pushback as long as it's not FB'ed and does a pretty good job of resetting the neutral with the distance and -2 frame situation.
I know this is away from the original point (and me rehashing), but you are spending resources to make that a go to option, and I still think there are options that serve the similar functions that are worth mixing in that cost nothing and can be less risky. Less risky starts to make sense when your life gets lower. B122 is -2 on block and leaves you close. At -2 you can be deliberately disrespectful with down pokes if they are initiating their turns a lot with slow moves or highs. You don't get all the push back so you can use both options to position them as needed. The MBdb2 to keep them away, and b122 to keep them close and for more pressure options.
One thing I was working on today was doing b2 stuff that lets you fish for an overhead that is -4 on block. It has the same "my second hit is an overhead" thing going for it that 21 does. The down side is it doesn't popup, and has slower startup that forces you to know when it's safe to use, and makes it a little easier react to.
The pros are that it hits mid, has better reach than 21, moves her in a little, and is totally safe. It has lots of active frames (2+22) so it appears to be a good meaty move. Fishing with f1's at a distance will leave you +10 on a stray hit which gives you enough time to go for a b2 overhead that will trade with -7f pokes, or just do b122 which nobody can stop you from doing safely. Hit confirming b2 into b211 is tricky, so that is a slight negative, but it's not at all unreasonable and basically lets you put out an overhead safely, that leads to a combo on hit. That's pretty cool. (For reference, the hit confirm works by always pressing b21, wait for the hit, and confirm the final 1 press. It lets you press the second 1 way later and it all works out pretty well and you never have to commit to b211 which is -9)
I've had to really try and drill these other options into my head over the last few days get them to come out in matches. Some of her strings feel super unnatural to do, but I feel like these are things that are working, especially against people that don't have a strong closeup game.
