Not a bad idea the % system but relies too much on chance. Maybe some steps like you can only have a chance to CC the ennemy when he's below 50% armor ?
If it works like you said, that would mean that a 99% armor left boss would have 1% chance to be CC and if you get that 1% the fight is so much easier...
I think the way it is is good but yeah, it could have some more ways to add armor or magic armor
