thresh buff
http://champion.gg/champion/Thresh does he need a buff
http://champion.gg/champion/Thresh does he need a buff
High mechanically reliant champions (Azir, Lee, and even Thresh) tend to always have a low win rate until you have a few games under your belt. You'll see that Thresh actually has a winrate over 50% around the 15-50 game experience mark.
I'd say no, he doesn't need a buff