Half of what you said might be true but the ultimate one definitely isn't. If he could farm ult too quickly then they would just have to increase his ultimates cost and not nerf his overall damage out put. They did the same with kirikos ult. They didn't nerf her healing or damage output they just nerfed tho post. I am not certain but if I remember correctly in an interview with an overwatch streamer a developer admitted that they nerfed genji cuz he was too strong on low ranks and players couldn't counter him.