I think anyone who saw the Intel Extereme Masters will agree with me.
Shen is OP. He was picked or banned EVERY SINGLE GAME, and generally, the team with Shen won, except I think 1 game.
These are the people at the highest level of play insta-locking or banning Shen in every game That's a big sign something is awfully wrong.
The big issue to me, watching said play, is his Ultimate, allowing him to join azny fight in progress, and go do his own thing meanwhile. Splitpushing and Ulting in at the right time to Taunt and tank is what seemed to be the issue. To be honest, Shen's Ultimate needs a complete rework, as your options are:
1: Try to take down Shen, which takes the other team 4 man push. Shen can ulti over to escape anyway.
2: Try to take the 4v5, only for Shen to drop in at the perfect time and turn it around.
While the skillcap to Shen is pretty high [You have to get the timing on your Ultimate right], it's undeniable that he's massivly overpowered in higher level play.