Blizzard have said on multiple occasions that the principly philosophy of the PTR isn't for game ballance but stability testing. You can't use examples from the PTR as proof, the PTR is hilariously unballanced due to a lack of player base and inaccurate skill ratings. You can't cherry pick examples of where buffs have gone through, I have no doubt there are just as many hero destroying nerfs that have gone through.

Also I find your logic interesting, you admit that bastion is underpowered then say he shouldn't be buffed? I also strongly disagree that bastion is one of the easiest heroes in the game, anyone who has tried to play him at a high level to some extend will strongly disagree with you; his sentry form is a massive sitting duck and for 90 percent of the game you'll be running away from enemy fire trying to heal. Compare this to any other defence hero; there's literally no point picking bastion instead of Junkrat, Widowmaker, mei etc. I feel bastion is currently facing a lot of negative predjudice from non-bastion players who havent spent much time playing him; and they're just thinking of that one time a bastion got a tripple kill on their team, they don't realize how incredibly situational and easy to counter he actually is.

Look as much as your initial knee jerk reaction is to these changes we really need to see them play out in a large scale setting to see their real impact.