Ashe cannot crit on Master Yi.
Wasn't one of the reasons you changed Sej's passive because she couldn't use permafrost on anybody that was slow immune or had a slow remover? True, Ashe can apply her slow more often, but she's still SOL if she's trying to fight a Yi with Highlander on or anyone with a bunch of slow removing stuff. Is this an intentional weakness, something you look to fix, or something you don't really care about?