In case you want to play on keyboard again... actually, this is for playing the game in general.
The game is impossible if you are not blocking constantly (left down). The key to actually playing the game is to wait for the gap in the opponent's attacks and unleash a combo at that precise moment. It's actually easier than it sounds, i think. When you think your combo is finished or you started taking damage, go back to blocking and again wait for the right time to counter. Also, save super attacks till the end for a quick finish.
Needless to say this does take some practice. Not mocking you or anything but Dash probably is the easiest character to play as well as Pinkie. Once you master one character, others seem not too hard...
... with the possible exception of TWILIGHT. As much as I love her she's a bit of a pain. Takes more skill to play as and one heck of an AI. Personally, I'm pushing her off until I beat the game with all the other characters. So yeah, hope this helps. Enjoy the game!