Apparently you can customize your runes to be, for all intents, immune to cc now. fun. Champions like Leona are rendered useless. And I mean USELESS! Riot, if you are going to add so much easily accessible tenacity via runes you need to add some counter balance and allow longer CC times even if just conditional. for now.
no, you can't be immune to CC. this is a dumb idea. You are saved. The end.
I get were the op is coming from, I was doing some calculations to determine max tenacity. I'll detail them here:
LEGEND: TENACITY (precision) and UNFLINCHING (resolve) :
Legend -- on max stacks gives you up to 20% total tenacity. Unflinching -- at best case is up to 35% tenacity *
Given a 10 second stun: 10 x ( 1 - .2 ) x ( 1 - .35 ) = 4.55 seconds
Actual percentage cc reduction of 54.5 %.
This isn't even counting in items such as : 
, 
, 
merc + legend + unflinching + iron = 10 x .7 x .8 x .65 x .75 = 2.73 -- 72.7% reduction
The question then is... since Sterak's is additive... is there any more cc??
Feel free to correct me if I'm wrong, I would really like to know!
