So after nerf upon nerf Shen seemed almost useless.... but I finally made a build that I actually like which compliments to his passive.

The main this with this build is to sacrifice a little bit of tankyness to do more damage so other team will focus on your more than your carries. If not, you will still be able to do steady amounts of damage to make them think otherwise.

There's only 3 rules that will make Shen (or any crc in this manner) beastly.
1. Stay alive
2. Kill or assist
3. Stay above lvl.

Easy enough right?

Shen doesn't need a ton of armor anymore, what he needs is a s-hit tons of health. He's more of a threat when he can deal damage than what he can bring as a tank, Riot successfully killed his viability as a tank. With this build, he is now a viable tanky-dps. One of the more OP versions of Jarvan and Mordekaiser mixed if you ask me.
The Hex-Tech Gunblade provides more AD, and the AP helps with his vorpal blades life steal. The item itself also gives life steal, and spell steal, which procs every time you use his Q "vorpal blade", giving you health back everytime it's used. This, and the item's unique active as well. It's like hitting 3 or 4 birds with one stone.

What I do is, max Q asap, at lvl 4 but 1 point on Feint, because you'll more than likly gonna need it for last minute escapes, till late-game. (yes I know the shield sucks but sometimes it can get you out of sticky sitations.)
By level 5, you should have rank 3 Q, and rank 2 E, you'll want to pick up R anytime it's available of course. By level 10 or 11, Q should be maxed, and E should be maxed or have rank 4, and R should have rank 2.

The item's I start with, is Dorans Shield.
Next, I pick up another Dorans Shield
Next, I pick up another Dorans Shield
I stack 3x Doran's Shield, and by mid-game, I will also have Merc Treads.
Once you have these basic set of items, which should be mid-game, immediately start building Sun Fire Cape (for the mere fact that by mid-game people like to start team fights thinking level 8-10 is team fight phase).
Since you'll have Sunfire Cape, you'll be able to farm more efficiently and deal more damage to enemies and minions alike.
This way, it not only helps in team fight's, but gives you a lot of health to synergize your passive.
Before the end of mid-game, you should also have a Negatron Cloak, Wit's End or AoL, Both helping Survivability, and helping with damage.
If the game last's long enough somehow, pick up Hex-Tech Gunblade, and your damage and self-heal + life steal + spell steal, will be insane for late game.

Of course, depending on enemy team composition, prioritize getting, Sunfire Cape, Banshees Veil, or Quicksilver Sash, way before Warmongs or Hex Tech Gunblade.

Also if you feel confident in your survivability, after your Negatron Cloak, get a Wits End if you want to tower push & do more damage more efficiently.

The reason I go for this build is strictly so I could farm minions effectively, even though I'm a s-hitty tank. People often don't think that Shen can deal about 30% of their health as damage in under 5 seconds until they see me do it.

9/13/8

Why???

9 in offense
for more punch to your Q + lower cooldowns

13 in Defense
It's pretty simple, get standard tank mag resist, & armor, but just make sure to get the dodge masteries, it'll compliment your dodge seals. That extra boost for speed is always a good thing. Make minions hit you, dodge, run towards your enemy, taunt, KI strike Voila, his health is below half.

8 in utility
After the latest nerfs to Shen, I find that to dominate and help do something for your team is, you have to stay above your enemies lvls. 3 on less time on death (just incase you need to ult, & very good for late game if you die), 4 on more exp. Preferably you need to stay at least 2 lvls above your enemies to become a threat, but the more lvls, the better.

Quints - Up to you
Magic Pen Reds
Dodge Seal Yellows
Flat magic resist blues - for early game mr

Exhaust and Ignite.

Why?

Almost all the time when I taunt a carry, they die. Taunt + exhaust + ignite + KI strike, Vorpal blade, auto attack = Kills or assist.

It makes sense to me why Shen should use those spells. He gets up close and personal.

This is just how I play Shen, but you can do as you will.

Learn how to last hit with Shen especially during laning phase.

I personally like Shen to solo top if your team has a jungler. There's only a few champs I would have trouble laning against with.
Annie, Karth, Ryze & Cait.

But even then, if I can taunt, exaust, ignite, vorpal. Their life bar will drop incredibly fast. I usually try to harass them to at least 400 hp before I try to finish them off. Even if you don't they will have to b, and that'll certainly give you the advantage of staying above lvl.