New Soviet Guards Doctrine

After playing the newest doctrine that has become available for the soviets I feel that it seems to be slightly under performing a bit. The tank destroyer call-in has a chance of either spawning two M10s or two SU-85s. During a multiplayer game I called this call in 3 different times and got the M10s each time. I believe after a certain point during the match m10s become obsolete against German panthers unless you can somehow maneuver around it, however this is rarely the case sometimes. Is there anyway that you can increase the chance of getting SU-85s so that the soviets have some way to counter axis heavy tanks?