Shaco is pretty balanced as is (evidenced by his barely above average jungle winrate - http://champion.gg/statistics/?league=gold#?sortBy=general.winPercent&order=descend&roleSort=Jungle ). Early game he has high damage, but his invisibility is very short, and on a high cooldown. Late game it's up longer and more often (as with every other champion's basic abilities), but his damage output falls off hard. It's a challenge for Shaco to even assassinate a squishy adc after about 35 minutes, because of the damage falloff he has. It's also worth noting that while his boxes can be annoying, they take a second to activate, do very little damage (unless he builds ap, in which case they're his ONLY damage), and can be seen with just a red trinket; something you should invest in if you're having problems with him. If your issue is that he can use them to block skillshots (hiding behind them, as you claimed) I'd like to mention that Heimerdinger, Malzahar, and Zyra all have pets on lower cooldowns that summon faster. Pets are common enough that it's just part of the game, not a broken ability. Shaco can be annoying, and is definitely a bit of a game health problem, since he isn't extremely fun to play against, but I think he is pretty fairly balanced.