Update on the SCH B -> 2 B+K series
It seems that Astaroth (due to different hitboxes ?) can ukemi away from you while making 2 B+K whiff (which other characters seem unable to do). He cannot ukemi to his right or left, it would still get caught by 2 B+K.
However, SCH B still is an interesting mix-up. You could well, use 236236B, since it's guaranteed (but costs gauge), but you can also use 6B to catch an Astaroth "ukeming" (yeah, a fine neologism) away. Therefore, even if you're facing an Astaroth player knowing this combo, you can still get some damage out of it. Particularly if you got your back to a wall. He'll be forced to ukemi away (the amount of devastation a SCH B -> 2 B+K -> w! etc... can bring is way too much for him not to get scared) so you'll be able to 6B him for guaranteed, nice and gauge free damage.