Eeeeh, that's not entirely true. I can't speak for stance switching in Injustice, but in MK9...it helped some moves to connect.
For example, when Raiden uses EX Lightning Bolt, it alternates between two speeds each time he uses it. I switched stances with him in training mode for the Hell of it and much to my shock - no pun intended - the speed of the second part of the attack changed considerably. Like, it hits faster than it normally would if you change from your default stance, but keeps you from starting a combo if your opponent is grounded.
Don't ask me about the above. I have no idea why it works that way.
For a more practical use in general, you could use stance switching as your way of "faking" movement, maybe provoke a reaction from your opponent. The mind-games, bro. It works.
By the way
STORMS - I vote keeping the block button to preserve MK tradition.