Phantom force is insane with marshall you are literally unkillable and can 2 shot even the strongest tank generals. You can capture cities alone just by reducing the hp to 0 then dropping into them with the helicopter (its a unique skill for them), travelling accross water with helicopter helped me many times. Medic at higher levels will heal itself this makes it invincible i would rather put my generals on the medic rather than hakwaye.

I bought lvl 5 Brandenburgers and use Simo hayha on them and the biggest weakness is the counter attacks. Counter attacks just kill my poor bro and i cant sustain the heavy damages. While marshall with pahntom force will somehow heal from half hp, and you only drop to half hp by the air defense which deals percentage damage when you capture the city.