Shen is not bad right now at all. You just have to realize that you really have no kill pressure early and need to farm and get gold to get tank items like Sunfire and SV. Then go for a BotRK to really make your Q do some large damage. You will always be useful at any stage in the game b/c your ult can drastically alter fights and allow your team to clean up and out right win a lost fight.
You will want 12/0/18 in masteries. Go for Fury, Expose Weakness, Natural Talent and Oppressor in the Ferocity Tree. Resolve get Unyielding, tough skin, Veteran Scars, Insight, swiftness and Grasp of the undying or strength of ages. Grasp is aggressive and Stength is more passive. Both are good on Shen.
Runes I run are: 9 AS Marks, Armor or health per lvl Seals or a mix of both, Scaling CDR Glyphs and MS Quints. These are completely based on my playstyle and can be tailored to your own but these are surprisingly good on him.
In lane your Q will allow you to last hit easily and you want to be pushed under tower. This makes it easy to set up ganks for your jungler. Don't underestimate your damage with Q. Even nerfed it packs a punch early. Also Shen's shield and Spirit refuge gives him a ton of effective health try to time your trades around your passive and W being up.