When I see B3/F3 I often just instantly do Parry, but doing it instantly only works with certain characters, others with a longer startup will make zod's parry whiff and I'll get hit for loads of damage, which is really annoying since you can blow up MB b3 or f3 if you time it correctly, putting them at a big disadvantage but vs some characters I end up disadvantaged instead. =/
oops super old thread...
I also keep parrying even against characters who are very likely to jump in or go low (batman, joker, zod, killer frost, deathstroke etc.)