Can Singed have MR per level please?

If he is against an AP top laner then he has to sacrifice his Armour/Mana items for MR which doesn't benefit his passive, or mana problems. He can build a and get health, mana, CDR and armour which is great for him against AD, but he has to rush a then when he's against AP mages, which barely benefits him aside from the MR. He is easily poked, he has poor gap closing against AP mages like and he can barely farm. He excels against AD top laners since they basically have to stand in his Q to farmand he also can itemize really well with meaning he can deal more damage, become tankier and actually stand a chance in lane. I am just not sure why he doesn't gain MR per level. I mean people like Nasus who has sustain and benefits greatly from the CDR, MR, and 20% enhanced sustain passive still gains MR per level. So please explain to me why not Singed.