Pantheons W passive is way to strong.
Pantheon has an amazingly strong passive but it can be very abused to the point where there is no counter play.
If your champion is auto attack based, pantheon will tank your first auto, if his shield is up. then W to stun you and block another auto from you the the shield it gives. Use his spear and E and an auto and gain ANOTHER SHIELD.
Pantheon has good ganks and early game potential. But his W passive is just overload. 3 if not 2 shields to turrets or auto attacks is just overwhelming. Yes CC and Mages can tear pantheon apart but he has gank potential everywhere. He will catch out your mage, and when he ganks anyone with auto attack damage, he just simply wont take any hits at all before his combo and allies kill you.