Sure Thornmail doesn't do as much to targets who don't do a whole lot of on-hit and crit alot, but Raudinn's + the master is pretty massive reductions of their damage.
Vayne and other on-hit ADCs got hit by the Thornmail change.
The ones who didn't really get screwed over is people Like Ezreal, Corki, etc. Kalista got hit by the thornmail change a bit. Not as much as Vayne did.
Lugg1 votesADCs got buffed across the board. Thornmail is worthless now and Raundinns is a bandaid.
67chrome1 votesbut Raudinn's + the master is pretty massive reductions of their damage.
The mastery point of crit reduction is canceled out by the mastery point of bonus crit damage, so that existing is kind of a moot point.
As for Randuins: 10% reduced crit damage is only a ~7.14% reduction in auto-attack DPS assuming IE and 50% critical strike chance. It's 0% reduced DPS with 0% crit, and a much smaller effect for most of the game.
It's also worth pointing out 
and 
with 
were the dominant marksman for seasons 1~3, and the AD-mages in 
and 
also had a really strong showing.
Most marksman are ability reliant enough that the amount of their DPS capable of critically striking is probably much closer to 50%.
Even ones that are heavily reliant on AA's like 
and 
tend to have potent on-hit effects that circumvent crit reductions.
As for Thornmail: I'm not seeing much of a buff. It does less damage to anyone with 167 total AD or more on Thornmail's armor, and less damage to anyone with 333 total AD or more with 200 bonus armor.
Thornmail is also still a really niche item that just isn't going to be purchased frequently and make a splash in a typical game. As a tanky DPS in top-lane vs. a Tryndamere that's obviously going to try to split-push 24/7? Not a bad item. In most situations - there are simply better items to run with though. Vs. someone like Vayne or Kog'Maw, you're still better off getting %AS slows, as you can actually benefit your allies rather than just yourself.
