So the question still stands, in you opinion is the Su-85 "far worse" than the JP? and if so why?
In my opinion outside of them both being 60 range TDs are incomparable as they serve 2 different sub roles.
SU-85 is meant as all-rounder TD with heavy armor counter focus with low mobility, but high reliability, especially against heavies and is a top tier TD for soviets so that reliability is required as there is nothing above it.
JP4 is meant to poke primarily medium armor and TDs(given its self spotting without crippling mobility and own target size), it does not need to engage heavy armor, because that's specifically what panther is meant for.
Given stats of both, they clearly aren't meant to engage primarily the same types of targets.
And both are good for their designated roles-SU combating heavy armor and JP combating all medium.
Cost can not be used as an argument as OKW pays 25 fuel extra for everything medium and above as a tribute for other perks of faction(while not combat focused, vet5 still provides much more utility, especially for vehicles compared to other factions).