You can't always react fast enough to interrupt or punish everything you might be able to interrupt or punish (A good FG player has a reaction time of 18-20 frames AT BEST, because you can't maintain this level of concentration very long). So it's very important to know your limits.
Test this if you don't trust me.Here comes the mindgame, basic example:
Iori does d.B (to force you to block low) and then his cross up b.B (because he can do it off a hyper hop only if you are playing a small char or crouch, from a normal jump it's too slow).
If you now he is going for this you can interrupt him with everything you want.
But if you think he is going for that you must do it as soon as possible after the end of the d.B blockstring.
Then comes two things :
d.B,s.C frametrap, if you don't have any normals which starts in 3 you can't hit and iori gets a combo.
d.B,d.B,d.B string : If you are getting up to do a s.A you are hit by the d.B who follows and iori gets a combo (d.B string can be delayed to be used as a frametrap).
Once you have understood that you can understand how thinks a Iori, if he is seeing you blocking low all day long he will go for his crossup and screw you up.
And if you are playing Kula use s.B instead of s.A to counter hops, better range, start faster.
In corner if he does something like hop C hop C you don't have the time to react, with hop CD you might just don't have the time to use a normal because of the huge blockstun (especially against a char like K'). So you are forced to do a dp in reaction or keep blocking until you can roll or interrupt him with a normal.
Break roll is a safe (good) option to get out of the corner easily.