Honestly, I don't find any properties of that string to be particularly applicable.
It's -8 on block and it looks interruptible with armor. The other thing is that it doesn't offer anything that 1,2, back 1 doesn't offer( difference is 1,2, back 1 is neutral on block and is easy to follow up with 4, grab n punch, which is one of her more reliable midscreen bnb's for high damage and it's an easy combo to perform consistently).
Keep in mind, I'm not saying there's nothing good about it, I just haven't found any applications for it that her other strings don't do better and reward her more for on block and on hit.
Even for whiff punishing, Sheeva could use Back 1,2, grab n punch/fireball and such, it has excellent range and can lead to a 22% combo or a standing position that leave you at + 7 if you do fireball at the end of the combo.