Yi, can not be slowed by Attack Speed debuffs.. is working how it's intended?

Saw the enemy team lock in a mostly ad team so I locked Thinking cool, vrs Yi and the others I'll E them and rush Frozen Heart BOOM. Help the team out really well with a smart counter pick. Do amazing in lane, shut enemy adc down np. Get to late game enemy Yi is so fed no one can 3v1 him without him resetting his Alpha Strike and him still winning. Think sweet now I should beable to tank him well, I mean I got And E which is another %50 AS debuff. And he just cut me down in seconds.. Watching his AS, it seem I did NOTHING to slow it down, is Highlander REALLY suppose to make it where he can ignore counterplay? I understand the Can't be slow running, but Attack speed? Really?! That just seems unhealthy. Thoughts? Riot plz