I really dont think he is OP .... My personal opinion on him being picked a lot and haching a good win rate is that hes not a simple one type support ... What i mean by this is if you look at blitz .. he grabs you and you could die... thats about it
With thresh he does more than just simple hook ... he has his W to pull anyone out of a bad situation ... good engage and good disengage through E and R
He just simply does more ... i always say why play blitz or leona when you have thresh who offers more at the cost of a slightly weaker engage