Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
It's early creep money/kills to mid-late game tanky-awesomeness.
After playing several games as Shen as a straight healthy tank, when he first came out, I was dissapoint. He could take punishment but it took him way too long to get there; also, he could assist in kills but couldn't take down a hero fast if he was solo'd in the woods, etc--at least not enough for me to like!
So get money--kill heroes when possible (and the move speed makes it very possible) and decimate creep waves. I find I'm a much bigger value to the team when I port in w/the ultimate and can actually dish out some pain besides just burning the taunt.
The attack speed works very well for quick money and last hitting: combine 21% atk speed, Ki strike, Madred's, and spam Q and you're a creep decimater! (not to mention lizard and dragon at level 5-7ish!)
So after 25 more games several weeks later, this is my optimum build: I've had 7+ games w/over 19 kills and as many assists.