Pantheon's ult is certainly OP. It's why he as a champion was made fairly weak with his most recent nerfs. He can go anywhere on the map, this makes split pushing a constant threat, and just like Shen, he can turn the tide of a fight. It takes a bit of coordination, and players who are bad with him will miss a lot, but the enemy only sees the targeting circle for 1.5 seconds, and with a moderate amount of forethought, it's usually pretty easy to predict where someone's going to be if they're pushing, or easy to hit people in a team fight. Ults like this (and TF's) are just OP by nature.