The link is to a list of a ton of bugs that shaco currently has. On top of this, shaco does almost negligible damage compared to the other assassins. Shaco needs more kills than all other assassins to stay relevant, on top of having to absolutely optimally farm every game. This is all terrible considering how hard his early game was nerfed damaging his ganking potential, and also considering the fact that he does not have a good clear at all. Yes. His first clear is strong, everything after that is horrible. This is because he has no aoe damage, damage reduction, or inherent healing in his kit, This means that you have to build tiamat, or suffer in the jungle because you cannot clear at all. This is horrible considering that if you cant build the item, or even if you do, you need to farm too much. Jungle will actually slap you, lowering your health so much that ganks are near impossible. This is because Shaco doesnt have the ability to force kills anymore like he used to. You deal almost no damage, just provide a small slow OR .5 second fear because of boxes ASSUMING, they dont know how to kill box, walk out of the way of it, or flash it. Plus, on almost all of your ganks, you are so weak that the laner can almost always force a turn and end up just killing you for forcing pressure. Which by the way, to have pressure, you MUST take ignite. It is not really a luxury because he has Q that he gets to take ignite. It is because he has no reliable CC aside from a small slow, so you need the ignite to get a kill. Speaking of things that you have to do to keep pressure, Shaco is one of the only junglers in the game that has to SKIP buying a jungle item to maintain perssure. The jungle item doesn't provide shaco with any useful stats that he couldn't get from another item. It gives him a little more jungle sustain, but the clears are too hard to make it worth buying. Shaco is supposed to be a jungler, but he doesn't function well as one. I get it, stealth is "OP". But really, this is so untrue. I would rather shaco have a stealth something like evelyn, but have more damage and reliable CC like her as well. The stealth is the only thing that makes shaco "okay" as a champion. This is because he literally can only clean up kills on champions below like 25% of their health with his stealth. But yes, in those situations, there is not much they can do. UNLESS, they used their free wards that they get every 60 seconds wisely. Shaco has all these weird trade offs that make no sense. One of the biggest changes that i think shaco NEEDS is a change to his E two-shiv poison. The thing about this E, is that it actually does ABSOLUTELY NO damage. This ability at max level when the enemies are below half of their health, ends up doing somewhere around 120-150 damage. Ryze, who can be 0-3 to my 7-0 on shaco, can use his Q two to three times in almost a 1 seconds window. These Q's will end up doing somewhere around 800-1200 damage total. Yes, its a skillshot, but not if he uses the rest of his kit as a snare and deletes you while you cant move. Seriously, if shaco can get 800-1200 damage off an E, make it a skillshot. Seriously though, why do Shaco Q, W, and E, deal 0 damage when building AD. When you go AP shaco, you at least get a small boost to the damages on these abilities, but most of your gameplay revolves around spending 60 second windows setting up traps that you hope your enemies dont counter with the free item that removes your boxes. Please riot, don't make the shaco community suffer or wait any more. We really need some changes. I get it, you guys don't like the champion and the way he plays. But this doesn't make it okay to leave this champion in such a bad spot for so long. Peruse the Shaco subreddit for even a moment, and realize how everyone thinks he has become so incredibly weak in comparison to before, and how everyone thinks that almost every other assassin to play in the game outshines this champion. We have played this champion for years though, he is fun and fits our playstyle. It's just clear that he is bad compared to the others.

Edit for some proposed changes:

1. Old passive was more fun, and better in my opinion. It would make it feel like his E and W did more damage, because they would be getting the bonus damage from behind on them as well. Some sort of change to denote that you were getting behind the back hits would be nice though. This shifts some of his power to his abilities while still making his autos feel strong. Also punishes people who just continuously walk away from shaco ganks.
2. Box changes- Just make sure that they receive their cc immunity that they are supposed to have. Also make sure that they have some sort of AD scaling that is useful. Maybe if you have more AD, make them activated (shooting) longer, or have more HP as well. Maybe even make ad give you CDR on it so that you can have more even though they deal less damage than AP. The biggest and most useful box change, would be adding charges to store up to 2 or 3. This would buff shaco in all builds, and make him feel much better to play. If you play AP, you could go back to lane and set up your boxes so that you were safe without waiting 45 seconds. If you were AD, you would have a little bit more reliable team fight CC, making you a little more useful. You would have a few more boxes overall, meaning that you could use boxes on each of your camps, making you take less damage and giving you a more reasonable clear. This would be awesome since shaco's clear is absolutely horrible, and the change would help him immensely by making it so that you don't come out of camps at 10% health and can actually gank.
3. E changes - The most important. Make this ability deal real damage. If the changes to passive are reverted, i think this ability would feel better in general. I think this ability needs some sort of actual execute ability. Not an increase in damage for lower hp enemies, but rather have it deal a percentage of missing health as damage. If this is really something that you think is too strong, make it a skillshot. Us shaco players are looking for more fun and interactive gameplay. Less autos, more abilities will make shaco feel more fun.
4. Ultimate changes- These are the easiest. Honestly, remove boxes from the after ult. We don't like them very much and would rather have something more instead. Maybe add a small fear to when the ult explodes instead of the mini boxes afterwards. Also make the explosion radius actually decent. It is so small it almost always misses if the enemy is just walking, or even kite attacking as any ranged character. If this still feels too strong, just make the clone a little harder to kill. (AND PLEASE MOST OF ALL - FIX THE BUGS) My clone should move or attack when it is supposed to. Randomly it will bug out on champions and dragons after casting. Particularly dragons and barons, if i ult, my clone literally wont move or respond to commands for a few seconds making the duration useless. Also, it wont attack any structures in the game by pressing R. only by Alt right clicking.

Additional Edits For some Suggestions from the comments-

1. A suggested change was a fear on the E the lasts about 1 second. People think that you should be scared of the scary clown trying to stab you instead of the little jack in the boxes that show up. I would be worried about taking the fear away from the jack in the box since it is so central to the play for AP shaco, but maybe centralizing the fear to like 1 second on jack in the box instead of 2, and making the E deal 1 second of fear as well might add more versatility in who you can fear and when. Another good change for the E might be to make the person nearsighted so that they cannot auto as easily. This would maintain slipperiness of the clown and add some fun new outplay options.
2. Another proposed change would be to rework Shaco's R in some way so that clones were more accessible. People don't like the shaco shows up behind you with 2 of him and delete you style of play, so i propose something different. Give shaco a clone that deals significantly less damage, but can be summoned more frequently and on average ganks. This way its harder to pinpoint and trade with shaco, but he doesnt burst you as quickly and as hard. This would give him a new skirmish potential, changing his playstyle, but still making him good,
3. A different ult suggestion would be to make his ult like Specter in Dota 2. He would have a longer Cd, but his ult spawns a clone of him on every enemy champion on the map. The damage the clones would do would be very small, but shaco could swap places with any clone on the map, giving him a better counter gank pressure while also remaining tricky and scaring his opponents.
4. More propositions include nerfing his Q, and im okay with this. I think changing shaco Q to some sort of seeable stealth or camouflage would be okay if shaco had more options/utility/damage in his kit elsewhere. People believe that shaco Q has too much power. I think that is fine to say and a fine trade off, but i would be sad to see the jump portion of this ability leave. He would still maintain some slipperiness if he teleported, but then went into camouflage.
5. Other options for Q changes without a rework - Somehow give him some CDR if he kill someone after Q or add a 1 second of movespeed boost or stealth after he gets a kill within a few seconds of stealthing. One of shaco's biggest flaws is that your Q is your only option to engage, but it is basically your only option to escape as well. If you fail to get a kill because you misplanned, or if anything goes not-according-to-plan, then there is nothing you can do but die there like a champ. R is not reliable in any way to escape, even with the ability to R over walls. The problem with the R falls into the category of good on paper, but not good in actuality. There are too many obvious indicators that the clone is the clone, from marks that characters leave on you before you ult, to the simple fact that the clone will take so much damage from one attack that it is clear which is which. All this not including the fact that many characters can just hurt both at once anyways.
6. More talk about the passive - The passive is really underwhelming because the crit strike is just a mini crit. It basically only makes it slightly more effective than an auto unless you are going AP.
7. Shaco E at early game is less useful than an auto attack during clear. The time you spent casting to deal 80 damage, is outshine by your 120 damage autos (not including the backstab). More evidence falling into the fact that his clear and his E are bad.

Thank you, and sorry for the rant. I hope for once, someone at riot would reply to this and give the whole community some hope.