W got changed because it was way too good on AD Ezreal. All of Q damage comes from the 1 total AD scaling anyways so you mostly rank it up by 2 to get it to the proper CD, because each rank only give 20 bonus damage. Each rank of W used to give 50 bonus damage up to a total of 280 base for 90 mana, that passes through minion and has a huge range. It also gave a 40% attack speed debuff to the enemy AD so you were pretty much guaranteed to win trade.
This build was fairly common among 1900+ elo for awhile and is the reason why everyone picked up Ezreal again, not because of Pulsefire. The only reason it got nerfed is because it's the dominant Ezreal build in every tournament for the past 3 months and they needed to nerf Ezreal/Corki/Graves who were the only AD carries that get picked in tournaments.