Actually pro players may have the deepest understanding of the balance but they only represent a tiny fraction of players and while useful for esports, implemen

Actually pro players may have the deepest understanding of the balance but they only represent a tiny fraction of players and while useful for esports, implementing their expert feedback may alienate the broader audience. QA may provide good balance feedback but are rarely valued for it/do it on their own time with career progression in mind. They often are a rare combination of players who also understand the dev side. For actual tuning before release, playtesting and other user research involving players representative of the target audience is the gold standard.