Removing his EXP bonus from the W passive would gut his duo lane hard enough to justify solo-lane buffs. Due to having to level like the normal marksman, he scales harder in the early-mid than them (in terms of itemization and ability power). Hence, his only choice is to survive the lane and hope to be useful in TFs as melee-carry, like in a solo lane.
I don't know why Riot persists to let this stupid passive. It was a bad decision to actually let him scale harder and faster than the enemy adc. Removing this adventage and let him scale hard, but at the same rate as the enemy carry, will fix his current oppressive state. Honestly, I didn't even notice the W nerf as hard as it should be. Mord scales faster and harder than the enemy carry and that isn't fixed yet.