As a Shaco main I think I see his strengths and weaknesses better than the average LoL player or member of the balance/rework team. This is why I have a few quality of life changes/a mini rework that I would like to suggest. Currently, Shaco is the only assassin that doesn't have 1) 2 dashes/an engage + escape and 2) any aoe. Take any assassin in mind and ask yourself if they don't have both of these, exactly, none. Next to that I would like to address some other small things that could help him out.
Quality of life changes:
First of all I would like to suggest to change his E making it adaptive instead of physical damage like it is now. This way it won't limit one of Shaco's play styles. On top of that I feel that the change of sweeper letting trigger Shaco's boxes was not needed and actually counters AP Shaco's whole play style since w/o your boxes set up you can't do much, might as well pick another mage. I'm fine with it showing the boxes as well as being able to kill them from range when sweeping, but they shouldn't be automatically triggered so that people that barely touch them w/ the edge of their sweeper ruin your box or multiple ones, otherwise they can just walk by them out of attack range and ignore them and then they'll die off on their own. Then another thing regarding the boxes, I would like to see their health scale with AP as well as most AD players can one shot them mid to late game which is too easy to counter the whole AP play style. Then his Q, ever since the rework Shaco has felt limiting early game since you have to put in at least 3 points into his Q in order to gank somewhat effectively w/o the enemy laner running away if yours doesn't have any hard cc as well as lacking damage with his e early, and this while Shaco is supposed to be a strong early game champ. I suggest starting the Q with 2.5 seconds at rank 1 (used to be 3.5 at every rank pre-rework), increasing w/ 0.5 sec every rank (unlike 0.75 rn) so that at rank 5 it's still the same duration (4.5 sec) as on live. Lastly I would like to address his passive being a crit. This limits him in building items like Stormrazor's since they don't stack or makes his passive useless when building crit. I think this should change to flat adaptive bonus damage (can still be the same percentage, just don't let it count as crit), so that Shaco has more variaty in the play styles he chooses.
Then, regarding his lack of aoe I would suggest to change his E to some sort of adaptive short range aoe damage (like Zed E or new Akali Q)so he isn't forced to build tiamat and that he also can kill more than 1 potential target if he isn't super fed. Then for his ult, which doesn't really feel like an assassin type of ult, yet is still one of his iconic abilities, I would suggest to make it that upon activating it you blink a distance comparable to his q where your mouse is when activating and being stealthed for 0.5 seconds (not enough to proc Duskblade a second time so that it wouldn't be too OP on him), but with the option of blinking back to his initial location when using R (where his clone is as well) within 1 second of using his ult so that he can still choose to continue fighting if he only wants his clone for more damage/dodging a damage or cc spell. This shouldn't be that hard to change since it's basically his q with a small Zed R dash back mechanic in it. These changes would overall put Shaco in a better spot imo, since currently the only way to succeed on him is to have unknowledgeable enemies that don't ward and taking Dark Harvest and hoping that you have a good start so that you can snowball off the Dark Harvest stacks. With this in mind it might be an idea to add some sort of visual effect of when Shaco is close to you when in Q, similar to Pyke W or Rengar R, only with a way shorter warning range like say 400 range so that it doesn't completely ruin his surprise element, but enough that an alert player can react in time to walk the other direction evading Shaco's backstab/aa. These changes will also make it that he will be able to properly build Stormrazor which will likely result into it being an additional core item next to Duskblade on AD Shaco, like with most AD assassins. For this I suggest nerfing his clone's aa AD scaling to 50%-60% instead of the current 75%.
I hope someone at Riot reads this through and does something with this/throws it in the balance team/rework team so that you guys can have a discussion about it, cause I really spent a lot of time thinking of these ideas and typing this out, as well as that a lot of Shaco mains would be happy with most of these changes (definitely the quality of life ones). As to any other fellow Shaco mains or LoL player out there reading this, I welcome any suggestions or discussions regarding my suggested changes.