Yeah, and even if you use blitzkrieg, you won't "render the su85 useless in no time" lol. If he is half decent he will reverse away and at-nade or button your p4.
Countering an su85 with a p4 requires one or more of the following
- su85 microes like shit and/or over extends horribly
- p4 player has perfect micro and no pathing issues
- su85 is not backed up by conscripts and guards
Of course points one and three will not happen if the russian player is above average skill.
Using p4 to counter su85 is just too risky at higher levels, and you are better off avoiding the su85 and waiting for an elefant or are stuck with using schreks or paks, which the su85 is actually not too bad against considering sniping the at-gun and/or pgren squad members. There just isnt a hard counter to it until you can field an elefant.