Sions Passive

I'm really confused... I tried doing a top lane on-hit Sion (I know, stupid move), and I noticed that my attack speed lowers when I go into my passive. Does it set it to a specific amount of attack speed when you go into your passive mode? Also, you lose ALL on-hit effects when you go into your passive? I'm really upset that it seems if you don't do AD Sion there's no way for you to play him (aside from tanky). Maybe I'm missing something.