The % increase in damage on Cutthroat never worked before, and he does a LOT of damage as it is now. Imagine that with an additional 15%.
They might have nerfed his early game slightly (not a big deal), but they had to tone his late game damage down as well because an extra 15% tacked onto what he was already doing was a ridiculous buff (and it was just a fix).
This way, he'll be doing around the same damage he was before.
I'm very passionate about my Scrolls. I love the way they feel against my skin in the moonlight.
His bases and ratios were from a time where AD casters had to have godlike bases and ratios to make up for their piss-poor item choices. The advent of AD caster items that didn't suck, coupled with his E getting fixed, made him stupid good and helped contribute to the AD burst assassin mid hegemony.