Can we buff Shen yet?
In the League of Tanks, Shen's really starting to show his age. Let's get down to the details of what exactly needs to be done!
His passive. Probably Shen's greatest source of damage past 20 minutes. This passive enhances Shen's next basic attack, causing it to do bonus damage equal to a flat amount, and scales with Shen's level and bonus HP. This ability is perfect on him, as it actually scales with items Shen will build. The issue comes with its CD, which is quite long. Sure, it's reduced when Shen auto attacks, which is great for laning, but Shen isn't able to stick to targets well enough late game to reap the full benefits.
His Q. This is Shen's main offensive poke in lane. Admittedly, it has no counter-play whatsoever and can be a real nuisance to whoever Shen is laning against. The damage and sustain it provides allow Shen to lane very well, but the ability becomes practically useless outside of laning phase due to the fact that it scales with AP, which Shen will almost never build due to his role as a tank.
His W. Shen's shield is a great tool for winning trades in lane, but like his Q it becomes unnoticeable the later the game goes because it scales with AP. Also, it's one of the only shields in the game that does not provide a great secondary effect when activated. Sure, it helps lower the CD of his passive, but that requires Shen to be constantly auto'ing and somehow sticking to his target the entire time. This reward is not instant like other shields, such as Urgot's, Riven's, Naut's, Lee's, etc.
His E. This ability, I feel, is completely fine the way it is. It provides utility, a gap closer, and CC all on one ability. It has many uses as both an escape and engage tool.
His R. Probably Shen's most powerful tool. I global ultimate that shields an ally and teleports Shen to them after a short channel. This is his identity, and fits his role well as a tanky guardian. It has good base values, and doesn't really need a change.
Now that we've gone through Shen's kit, let's talk about the issues of it. His passive, Q, and W feel like they were designed exclusively for the laning phase. His passive is too hard to proc more than once in teamfights, and he relies on the base values of his Q and W because they both scale with AP.
So what needs to be done? This is a tricky question, because straight up buffing numbers will make it even more anti-fun to lane against Shen. My first suggestion would be a change to his passive. A Sheen-like effect would work very well with Shen. Give it a static cooldown (3 seconds being an example) and make it so that it only enhances his next auto after he's used an ability, while letting it still scale with his HP. This gives Shen a more reliable source of damage in the late game as he won't be reliant on auto-ing non-stop in order to proc it again.
His Q is a tricky ability to balance without making his laning phase god-like. One approach could be to make it a skillshot, then compensate that with allowing it to scale with HP, at a small rate of course. This makes it a lot easier to play against Shen, as you won't be eating Q after Q after Q because he can no longer reliably hit you whenever it comes off cooldown. But in the case that he does land it, it'll now do more damage and will actually pose a threat in the late game.
Shen's shield is arguably the weakest in the game. It doesn't scale with any items he builds, and has no secondary effect that immediately benefits him. An easy fix would be to make it scale with HP like Naut's, but I don't believe that is the best approach seeing as his passive already scales with HP and the change to his Q would do the same. Leave the AP scaling, maybe buff the base values, but give it an impactful effect while the shield persists. There are a lot of directions that can be taken when deciding what secondary effect to give it. Bonus magic damage on autos would highlight Shen's lane dueling. Having his autos slow enemies while the shield is up would give him a source of CC outside of his taunt, and would allow him to focus down carries in teamfights.
Keep in mind that these are all my opinions on changes that need to be made to Shen. Buff Shen 2k15. 
