Updated the thread a bit. Starting to get the feeling any string with a gap can be backdashed, but I don't want to jump to that conclusion yet, considering harley's 11*2 string has gunshots that could catch a backdash.
Other:
-batman's 11*3 can be mbb3 punished (known, but not done enough in play in my opinion)
-Green laterns b1*2 can be mbb3 punished, while b1*3 cannot