Fiddlesticks rocking a 56% win rate in the jungle and everyone jumping here to defend him and downvoting this thread to oblivion.
Yes, OP is lacking reasoning (guess the downvotes are warranted). Fiddlesticks did receive an evident buff though, and definitely needs to be toned down a little. Not sure why they put a MS boost on a champion who often stands still for a while. His ult was already quite devastating in the right situations, so it's no wonder that putting an MS boost on him is making him win so much.
I mean, the champion has been outright broken in ARAM forever. If a champion is that strong in a different mode, there are obviously circumstances that could easily lead to them being OP in the main made. Throwing him an MS buff is one such circumstance.