Why did Master Yi get a buff

Why did you nerf one unstoppable, late-game scaling true damage hyper carry with frustrating mobility put into their Q and an ult that grants them a crap-ton of damage and movespeed

Only to throw an unnecessary buff at another one

In my opinion, a Broken Yi is far worse then a broken vayne. Yi has built in sustain, damage reduction on his Q, and while vayne can Q to dodge skillshots, Yi's grants invulnerability. You also didn't just 'nudge' this kit strength, you buffed his damage significantly. 10% AD ratio increase is spicy on any champion, but when that is coming out in true damage its absurd.

Yi's Q allows him to dodge quite a bit of CC, and you can't exactly slow him since his ult is so counter-play heavy (sarcasm). His built in heals (not to mention bort is very commonly built on him) combined with his Q allow him to pop out of a CC that actually lands, Q again because its CD is relatively low, and continue to shred.

Yi's only counterplay, is to hardlock him down and shred him before he can burst you. As a support main, Yi is "T minus X seconds till ADC death", and with so much more damage, this window of opportunity that I have to stop him before he gets a kill and reset on his CD's is significantly lower.

its almost as bad as Olaf when he's over powered. It feels like I'm trying to use a slingshot to stop a bullet train from ramming my mother into the next dimension.