The difference is that TF and Pantheon are capable of a lot of burst damage and can use their abilities to just chop away at someone's health like nothing. Shen is a tank and relies on taunting and taking all the hits for his teammates.
As long as the attackers of whoever Shen is ulting aren't complete retards, it's almost always used for either teleportation or purely defensive purposes. And that's what a tank needs, to be defensive and to be mobile.
They're different but the problem remains the same. Split pushing is far too strong (And way too fucking lame) a strategy and it shouldn't be something that's encouraged to be done by introducing characters that have such powerful effect to a team fight directly and indirectly as a result.
A team with Shen is almost a guaranteed victory in many cases since, as described, Shen can split-push a lane for free and if the enemy team initiates on his, then not only is he still in the fight, he's in the fight with a 1,000HP shield to the AD Carry. If they don't initiate, then somebody is stuck having to go deal with Shen, who, as he is now, can surprisingly deal with most people in the game solo simply as a result of his ridiculous sustain and damage absorption. Meaning they still don't get anywhere.
Edited:
Basically what I'm saying is you always lose no matter choice you make.