CC should count for mastery and get a tab in the end game stats.
Ive always wondered why there wasnt a "time CC'd" tab in the end game stats.
Playing someone like Leona who can lock down a whole team with a great ult and get 2-4 stuns from Q in a team fight and the small lock down while you E to them several times during. Thats a ton of time the enemy isnt fighting back and giving your team time to kill them. Her help doesnt come from her damage its the time cc'd so why isnt she rewarded for taking the enemies out of the fight for so long.
Mastery and end game stats should take time that you stunned, slowed, rooted, silenced, knocked up, the enemy and give credit where credit is due for your help. Could drop slows and soft CC if they really wanted too but at least count the Hard CC