Sated Devourer completely ignores some on hit effects

I was trying stuff out in a custom to see if there were any champs that had funny interactions with sated and i was surprised to find that some champs with on hit effects just don't work with it. I was thinking that since Taric's passive does bonus damage on next auto and reduces his cooldowns by 2 seconds sated would proc the damage twice and reduce his cooldowns by four seconds, but sated completely ignores his passive. Am I wrong in thinking that his passive is on hit?