The problem isn't the Quad, its that Ostheers supposed counter, the 222, is unable to take a bullet from anything. All the 222 needs is an appropriate amount of armor, either by default or through a munitions upgrade.
The vulnerability to small arms fire of all kinds it what imperils the 222 so much and renders it ineffective against everything except for ambulances and katyushas. If the 222 had to stay the same health and armor wise, then its autocannon needs to be effective against infantry ala the CoH1 default puma.
even assuming the 222 got buffed, there's still the su-76 and the t70 in the same building. the soviet light armor are just never meant to arrive this early. the ost just doesn't have any equivalent unit without doctrines.