I have had many ideas on Shaco over the past years and I greatly appreciate you Meddler for giving us info on the changes to him.
I would be pleased if you would read over my below comments on him 
PASSIVE-BACKSTAB
Shaco deals 20% bonus damage when striking an enemy from behind with his basic attacks or Two-Shiv Poison.png Two-Shiv Poison.
Q- DECEIVE
PASSIVE: While DECEIVE is not on cooldown, Shaco's basic attacks poison his targets, Slow icon slowing them for 2 seconds.
ACTIVE: Shaco instantly blinks to the target location and stealths for up to 3.5 seconds, also causing his next basic attack within 6 seconds to slow for 2.5 seconds.
SLOW: 10 / 15 / 20 / 25 / 30%
W-JACK IN THE BOX
No major changes
E-TWO-SHIV POISON
PASSIVE: Minion and Monster miss chance: 20 / 22.5 / 25 / 27.5 / 30% (Doesn't Deactivate)
ACTIVE: Shaco throws up to two daggers at the target enemy, dealing magic damage. Both thrown daggers apply on-hit effects.
MAGIC DAMAGE: 30 / 55 / 80 / 105 / 130 (+ 100% AP) (+ 100% bonus AD)
R-Hallucinate
No major changes
- His E seems to be used as a way to secure kills when enemies are running- which is great, but the slow portion of it normally doesn't last long enough to catch up with the target.
I feel like this might not be optimal for his kit. It seems like it would flow better if the slow portion of his E is applied to his Q. That way if he uses his Q ( For surprise or as a gap closer) he can slow for a second or two but sacrifices his perma slow. This seems to make more sense and I feel it would have more competitive play.
Another thought- if the E's damage was lowered, but he was given 2 shiv instead of one (since he has a shiv in each hand); I think his play would be more fun.
Also, I feel like his W fear and box priority could use a little changing when it comes to fighting champions.
Let me know what you think, and take an and leave whatever you might could use :D
P.S. On a side note, I have slowed my play on him because his scaling isn't great. Right now Vi, Hec, Kha or Rengar all can assasinate and are so much more valuable late game.