Against the AI, I've not found this to be an issue vs medium tanks, but i do have an anti tank support company. Against heavies, well, i don't see any most games. I think i saw a Tiger late on in a France game, but the fact i couldn't pierce it was offset by the fact it was surrounded and cut off and out of supply. Again, by late war, you will have the tech to make 13.2kph medium tanks, which you can start adding to the light armour divisions, as well as gradually start replacing the moto for late war, high speed mechs. 4 LARM 1 MED 1 MECH 4 MOT with anti tank support @ 13.2kph is a formiddable unit, with good hardness.