Look into a mirror and read back what you wrote to me.
Yes it could have been less harsh but from a balance and playability standpoint it’s not good to add easy mechanics that are inherently powerful. The truth is it is an extremely thin line between strong but effective and overpowered when it comes to “simplistic” characters.
His nerf was 15%, they could have tried 10 or 5 but the reality is for most it would still probably feel too weak or too strong. If him being balanced is resting on exactly one mechanic and that mechanic is causing the entire playerbase to be frustrated from “free” power given then the choice is simple. That is why Bastion is a niche character, because the only way to make him a generalist or usable in every situation is to make him super strong.