Shen mage or tank?

Hey riot, quick question. Why the hell are Shen's main abilities ap scaling? When is he ever gonna build ap?.................... Its so useles even when you do build ap because there are to items that would work for him........ most of the major ap items like deathcap and ludens would make him way too squishy. He does so little damage with items like nashors that's there's no point in build it. And when you choose the hp ap items its still not enough durability or do any damage to the other team..... The ap scaling on him is so useless..... he might as well not have any scaling at all..... Please explain the thought process behind it.