If enemy goes turtle mode with ISU152/IS2/SU85/SU76, use it, it will annhilate them.
If enemy goes mobile force with mass T34, T34/85, DONT use it, because it will likely be flanked (believe me). Instead, use Panthers or Tigers, or do like me and get PaK43

Remember that next patch is adding HOLD FIRE, so it will be more beastly.