It comes down to the fact that this ISU is nothing like the previous one.
This one needs micro and attention
This one isn't the way to go in 80% of the games
This one isn't better than going for t4 and get su85's or other things
This one isn't the beast it used to be.
The fact that the unit changes and gets a an other role in the game, is in fact also a part of balancing. Its not that easy to use.
Its not always about changing AoE, range or splash, its also about other solutions that reduce the impact of a certain unit.
So you are okay with this unit to be completely useless?
The jagtiger will now never be able to kill a single sherman, or pretty much any vehicle for that matter.
The ISU-152 will still be able to oneshot squads, but will be completely useless againts vehicles.
I really don't see how these changes are better than just straight up nerfing the AOE on the isu and removing the ability for the jagtiger to shoot through buildings...
And it doesn't need micro and attention. It is simply not possible to hit moving targets.
And overall, this will lead to axis being more OP in teamgames, because the sheer OPness of the isu-152 allowed the allies to fight back in big team games, since all of their other options except ISU-152 are inferior to their axis counterparts, it will be even more terrible.
The sole purpose of the jagtiger was to pretty much to counter the ISU. Your just fine with tigers/panthers/KTs to win.
It's ok though. Eventually relic will realize that this change simply isin't a good idea.