Yea.. I don't get how anyone doesn't see this change as a buff. It's 80% of the damage AP Yi did on alpha strike, combined with the melee damage AD yi always did. He gets Q and E resets whenever he gets a kill, NOT just when his ult is active, btw. If he gets one, or an assist, while ult is up it extends the duration of the ult AND takes 18 seconds off his cooldowns.
Yes, the scaling on alpha strike is a little worse with AD versus the old AP, but you get kills easier in the early/mid game, so you get to that unstoppable burst point quicker. Previously, Yi sucked until he got fed and could practically one shot squishies with alpha strike. After that, how fed he was at a point of the match was irrelevant. It doesn't matter if you do 100% or 200% of a squishy's health, if they are dead they are dead. So, past a certain point his AP scaling didn't matter, it was only until he got up to that high burst point.
Now, scaling off AD, he farms the jungle or lane much easier.. gets items faster, and does more combined damage on his ganks since his auto attacks are chunking people along with the alpha strike. Doing 100 dmg, for example, less on his alpha strike now versus AP YI before doesn't matter, cause your auto attacks/passive/E does that much and WAY more if you activate E and R.
Seriously, the change boils down to, BIG damage buff at all stages of the game and a nerf to his late game 'invulnerable meditate tank lulz!' bullshit. His damage gets so crazy, combined with his resets, though, that it doesn't matter. You used meditate to stall for another alpha strike to come up and hopefully get a reset. Now, you just melee the squishiest/lowest person once or twice to get the reset.