Data is simply an outside look and also a number. It does not tell you the full story of the champs strengths and weaknesses, and whats causing them to be strong or weak. Wake up. Its 2019. Whats the point of a playtest team if the product is gonna get more shittier because they aren't being used for a better thing: Helping determine what ACTUALLY needs nerfs in a strong champs kit.
You nerfed Eve Q when the real problem with her is her W.
You nerfed Aatrox because he's good in pro play despite the fact his kit is better in pro play in general based on design.
AP items are so heavy cost efficient that you could literally sack your build and rush Deathcap and Void after a Zhonyas and still be OK.
If I actually joined the team, I would study not only the data but also the kit, how it works, its ideal power, and how it feels to play it IN GAME.
It frustrates me time after time when these screwups keep happening. Pro play isn't gonna solve most of the balance issues that are in this game, accept it already and start working on fixing it.
You have to balance the game by how the champ feels and works, with winrate/pickrate/banrate being considered. You dont balance with just winrate/pickrate/banrate alone.