I think Brumbar is fine aside from veterancy requirements. Brumbar is amazing when supported with proper AT. Also, Brumbar range nerf was needed due to Jager doctrine being super cancer with scopes and elephant in the mix.
TBH I dont think infantry changes for late game will help. The problem becomes with MP bleed and excessive amount of fuel. The Brumbar is more than enough late game to kill Allied infantry.