We nerfed Shywana cause she could push lane and trade simultaneosly

Hecarim has mana costs

Hec can trade with tier two boots @@?

One too many v.

They nerfed Shyvana because she was resourceless, innately tanky, had ridiculous damage with 0 offensive items, mixed damage that needed 2 items to build against, pushed lane and won trades thanks pressure and few could have the tankiness and damage to actually defeat her.

Overall she was a metagolem that won lane by being obnoxiously tanky with big bases mixed damage.

Hecarim has mana, but can reach that level of obnoxiousness in match, yes. But he is also way squishier early and has no ranged poke.