Most of your concerns got covered already (range increase/time to disable ability etc.), but there are two aspects left:
But in real life games this is almost never happening since soviets have those "balanced" satchels so going close to the SU85 is guaranteed p4 death.
1) Satchels: Of course they are strong and they will criple your tank seriously, but they are very short ranged and Penals have no sprint ability. If you see them you can cancel your attack in time. And its the same vice versa. If you flank a Stug with a T34 for example you always have to count in that there are Shreks, a PAK or/and Grens with snare nearby. Flanking is always risk versus reward. But of course you have supporting units too, which can support your attack.
Even without the satchels, just a regular AT nade will stop the p4 giving time to the SU85 to rotate.
2) Conscript AT-Grenade: AT snares don't damage the motor of full health medium or heavy tanks anymore, luckily that was changed a while ago. So AT-Grenade is completely harmless unless you don't get hit by the SU-85, a nearby ZIS or another tank first.