The main problems with the old 76 mm were:
- powerspike of 2x76mm timed attack with Combined arms
- because of the RoF of the AP shell it wasn't necessary at all to switch to the AT shell, because the lower penetration chance vs heavy tanks was equated but the RoF. In the end AP shell had similar DPS vs heavy armored targets and higher DPS vs all other targets including infantry of course
They should have just removed Combined Arms and replaced it with an offmap ability.
With the nerf to AP RoF 76mm got worse vs infantry and lightly armored targets. This should have been compensated by other means like buffing AOE of AP shell. AT shell could have 50 range to make it more appealing in addition. That way 76mm would have stayed unique and maybe more of an alternative to the Jackson/M4A3 combo.
In the end 76mm is at the same tier as Jackson, only 20 fuel between them. If major fuel cost would have been split in two parts somehow and Jackson would come later than all Sherman variants as a heavy tank counter, the 76mm would see way more action without another single buff.
The point was to nerf the doctrine in any ways, mot making it different.