Irelia has at least two unnecessary strengths that are going make balancing her more difficult.
1 -- Her W can't be interrupted.
There is no good justification why a Diver/Slayer hybrid should have an uninterruptible damage reduction channel. It's not just bad gameplay design, it also reduces counterplay against her scaling with her skill cap, and we all know what how much players hate mechanically high skill cap champions, especially when they're mobile (Yasuo, Zed, Fiora, historically Riven, etc).
2 -- Her E activates itself after a delay.
Again, she can mitigate CC by dropping a blade before she's hit and letting her E stun any melee attackers who get too close (because her E has a broad range). Afterwards, she gets a window of power from her E mark, letting her turn the tables on anyone who tries to counter her.
Do you guys want to create balance problems for yourselves? Are you worried CC is being too influential on balance or what? is Kai'Sa's win rate too low?
Some kind of defense for her design would be nice.
