Auto-overcharge is a nice quality of life feature that manages to both allow simplification of the game for newer players, and also add more complexity/depth since it adds extra decision making re whether to use auto or manual overcharge.
It's clearly weaker outside specific scenarios where you want to overcharge while moving (e.g. to chase down an enemy ACU or avoid being chased down), since against T1 units it can waste the OC against a half-health T1 unit (instead of getting a clump of them via a manual overcharge), and later in the game you cant overcharge as much with it as with manual overcharge.
It was a nice crutch during my earlier sub-1k days, but I quickly moved to using manual OC most of the time, with auto-overcharge now used very rarely (outside the specific scenarios noted above) where I need the apm for something important, I can afford to waste energy on poor overcharge shots, and my ACU isnt in imminent danger.
It sounds like the complaint is more about the power of overcharge against T2 units, but that's an issue with overcharge itself as a mechanic, and if anything auto-overcharge makes the problem slightly less severe since if a player relies on it they're more likely to waste an overcharge on a T1 tank when T2 units are nearby.
Meanwhile nerfing gun damage encourages passive ACU gameplay (why take the risk of losing the game for such a small benefit vs the current scenario where taking risks with your ACU gets rewarded), makes it far better to go for T2 upgrade over gun, and makes overcharge even more powerful than it currently is (since it will account for a far greater proportion of the ACUs damage output).