I think Shen's kit overall is really outdated(just wanna share some insight).

First, I'm not here to say he is weak/useless etc, nor that i think that he needs direct buffs just by increasing his numbers, i just feel that his abilities could be changed in a way that would make his maneuvers to flow better, and his gameplay more dynamic. This is NOT a "give me buffs" topic. Another thing is, these are just some food for thought, and that none of my presented ideas are what i necessarily assure to be the most perfect way to approach the champion(feel free to disagree). If there are Shen's mains out there, i would ask you to read and see if you agree(or not).

His entire impact imo relies on his "e" and his ult, both are decent skills so i won't complain about them directly, but about the fact that in the absence of both, Shen is almost a glorified minion in the terms of real impact. If a fight breaks out and you for some reason miss your "e", for the next few seconds you are pretty much there(at most you can sponge some turret damage).

I will start with his "w", this skills pops a small shield that absorbs so feeble amount of damage for 3 seconds(unless you a build full ap, which is not a very good idea), the 1 second reduction on his passive CD for the most part doesn't even have time to proc, since the shield is gonne as soon as it come out. With that in mind, i think his "w" could be made into a more reactionary skill(like Sivir's shield), instead of 3 seconds, make it like 1.5 seconds, but, if an enemy land an autoattack during that time it could absorb that attack and reset his passive, or maybe give him some temporary extra defense or something else(which would synergise with his taunt as well).

Secondly, his "q"...like his "w", it is what it is. It's small damage targeted spell that heals for a small amount if you follow up on autos(useful early on for lane sustain, almost non existent later on). What about increase the range and make it a skill shot instead, if you land it, you mark the target and for the next few seconds you gain some movement speed towards(only towards) that champion, if you land your Ki blast while the opponent is marked, it deals some extra magical damage and consumes the mark.

Raw numbers, cooldowns and whatnot, is beyond my territory, so i won't discuss that. These are some ideas that i think that would make Shen learning curve higher, but, if played right, he could be more impactful.