So I checked the PBE notes on Surrenderat20 and I see that Shaco has a few changes on the PBE with no context whatsoever. The first change was to his passive changing it from 120-145% to 130%(40% AP flat). The second being that the damage was removed from Q and the cooldown was changed from 14 at all ranks to 16-12.
It seems to go after AP Shaco's burst slightly in that his AP ratio on Q was amplified by backstab and now they're moving the damage from Q to the passive to give AP Shaco more DPS rather than burst. It seems to limit how much Shaco can Q early as the cooldown was nerfed on early levels as well as no longer having base damage on the Q. On the other end it seems at level 9 Shaco will be more mobile but have less damage coming from AD later in the game as backstab was tuned to be 130% flat throughout the game rather than 145% late and will increase Shaco's reliance on tankier on-hit builds such as Tri and Deadman's Plate.
I know that Shaco has been in the top of the win rate for quite some time now, but I'm still curious why these changes are in place. He's strong but not seemingly out of line. I know I most likely won't get an answer from a Rioter (which would be nice to get actual context) but I'd at like to at least discuss why these changes are in place when he isn't even strong in a competitive setting.