Yeah it's kinda hard, i mean first you have to pres x, then x again, and x again, and finally Y. I was tryiing to do it the other day but i just couldnt remember the order so i jsut wrote it down on a post it so i could refer to it when needed.
Some games, like MK2, you have to just jam all the buttons as fast as is humanly possible. This is not the case in CC, where the character will not remember previous inputs, but rather will simply do whatever you're telling him to do at the time as long as he's not in the middle of something else.
The magic combo is more like X-X-X, brief pause, Y. Just hit X until you've counted three hits, then start hitting Y. Ta DA!
FYI - there is an XXXYY combo which unlocks at 50, but until that time XXXYYY is also a viable combo.
I agree that the magic combo attack is based on if you're at a certain point on your magic stat. I believe it's the 3rd sparkly bar marker (cause outside of a stronger basic attack I've seen no other new skills). I do not believe that it's based on what level you are like the normal attacks.
As for how to do it, you have to make sure that you're not in range to grab your opponent, but close enough to hit them....and it does a short range splash damage as well (using the blue knight, I've frozen 3 guys charging at me from straight ahead with this).
What I like about this attack is that with other characters that has no elements(Arrow magic,saw magic,etc..)it just does a lot of damage. I can do 200 damage with my Industrialist,so I guess it's better than magic attack.