Irelia - Not understand how she is balanced

I just don't understand how she is balanced. It seems like most of her kit need tweaks. For example her passive, It should be 10,20,30% with 10 being minimum. 40% in my opinion is way too much, especially for a passive, 30% max is even pushing it 25% sounds like what it should be.

Irelia true damage is high. Max at 75 is high. So I am a tank and being a tank basically means jackshit against Irelia, just it would take her longer to kill me. Which she can stall out with her cc if she is lower than me, or slow me, and sustain with her passive restore (Not much but I am a tank), then her ult restore and so on.

I also don't see how her ult is balanced with a 50 second cd, so you're basically telling me she can use it once a minute.

I really don't see how her kit is balanced, I remember when I use to play her I 1v5 the whole team because she is that strong with her dive, her cc, her damage. Which mean if you're squishy you're dead instantly once she jumps on you.