Not so much a nerf as it is a shifting of power.
They're going from RNG burst per second to slightly less burst per second and more DPS.
Basically, more predictable damage. If you know the ADC only has a Razor +1 other item it's safe to say that they aren't gonna be doing much in an extended fight where they can't back off and wait 2.5 seconds for the passive to reset. Look at that! Counterplay to autos!
Seriously though take a second look. As a top lane main I hate ADCs and these changes ARE good changes.
Zeal cost +100g.
Zeal upgrades +200g.
Infinity Edge no longer has crit chance or the crit damage passive but now has crit chance doubling and "crit conqueror". This means that IE alone is basically worthless now and absolutely REQUIRES one of the cost-nerfed zeal items. In addition to this, the item is going to do less to squishy targets on crits.
Razor as already explained is weaker in extended fights early on but good for poking. Later it simply functions as an item that grants 25% AS and 8% MS.
Essence Reaver is the only one that looks shaky to me. 20% cdr on basic abilities PER AUTO (granted it requires ulting) sounds absolutely busted on a wide variety of champions.
Q permanently up and mana cost semi-negated.
Ulting, using E Q then W will nearly reset the cooldowns of all 3 of his abilities so he can do it again.
= All his abilities are up 60% faster (more counterstrike, more screwing over auto attacks).
= Hilarious no cooldown Q and W for infinite chain CC lock trolling a single target lmfao. (press R then cancel)
= YES. THE MAN-GOD NOW HAS NO COOLDOWNS WHATSOEVER LOL.
And ofcourse this chick is gonna abuse the hell out of it: 
The possibilities...