Thresh does need nerfs shift defensive power from W into R
The problem with him is that he becomes furtively tanky after alot of souls and b8's you then cheeses you with his stupid shield and there's ALOT of instances where he SHOULD be dead but he lives on instead. My suggestion is shift his defensive power into his ult from his W.
Dark Passage:
Shield Strength: 60 / 100 / 140 / 180 / 220 (+ 1 per collected soul)
change to
Shield Strength: 60 / 80 / 100 / 120 / 140 (+ 1 per collected soul)
The box:
Magic Damage: ~~250 / 400 / 550 (+ 100% AP) ~~ 200 / 300 / 400 (+ 50% AP)
Add both magic resist & armor scaling to the dmg not sure how much