According to riot, it was not removed because it was op. It was removed because it was deceptive. While he was jumping the animation for his w would spawn on his model, but the hit box would spawn from his hit box on the ground. The animation would not sync up with the hitbox, so people got hit with damage they could not see incoming. Fixing it would have had the animation spawning from a point below him on the ground, which would also be deceptive. That was Riot's argument when it was removed. I'm not sure it was so unfixable, but there you go.
This wasn't a problem for rengar because his model stays low to the ground and the jump is fast enough that the projectile and animation still sync. Same for nocturne,