Well, for a champion with an overloaded kit containing almost everything you could want in a fighter/skirmisher, being damage reduction, insane mobility, a stun that allows for more mobility, an ult that allows for more mobility; slows and has a form of "CC" that completely invalidates a damage source, and a passive that not only gives attack speed AND AD but also shreds through shields like paper; she sure does lack any form of consistent counterplay.
So, the only counter to Irelia is to CC her....but guess what, she can still channel her W (damage reduction) throughout the entirety of the CC. Oh, and if that wasn't enough she **also** builds Sterak's, so CC'ing her is pretty much pointless.
Yeah, that -5 movement speed **reaaaallly** made her impossible to play. She's too weak guys, far too weak. Like, that 5 ms is so meaningful on a champ that already has an abundance of mobility......
With that said I'm going to spitball some ideas to nerf her, some more drastic than others (obviously not to be done all at once):
* Remove the Q mark from her E
* Correct E's hitbox (it's really forgiving)
* Remove the bonus damage Q does to minions and as compensation add 5-10 damage to each rank.
* Increase the cooldown of her ultimate
* Make W cancel-able by CC
* Remove the damage reduction from her W
* Nerf her passive's bonus attack speed and/or AD
I will say that E's hitbox being corrected is a necessity, because right now it's ridiculous (similar to Lux Q's hitbox).
Anyways, Irelia **needs** to be nerfed, she's easily THE single most broken champion in the game. Akali, Graves and Jax don't even compare since they only really have 1-2 aspects of their kit that make them broken....Irelia's ENTIRE kit is broken.
tl;dr -5 MS DID NOTHING NERF HER PROPERLY!!!!