With long range, high penetration, deflection damage and powerful AT shot ISU-152 has great AT even if its AI performance is even better.
It's not great. It's ok. It is not why you would get the unit, you don't get an ISU to hardcounter heavily armored german tanks in the game. You get an cheaper and faster firing SU85(or 2, considering the ISU costs roughly twice as much) for that. I would only use AT shells if my SU85 was destroyed or out of combat.
Once again, other people put it better than me:
The more you need to shoot AP rounds, the less your ISU will pay off. SOV has better AT options than the ISU, and even if you compare it to Axis units that need to deal with often different unit designs the Axis tank performs better.
The more you have to use your ISU as AT, the less it will pay off.
If in your opinion it is not "great" I am fine with it, but saying that ISU-152 should be used Only for AI is simply BS.
Using it only for AI will grant you the greatest rewards the unit can offer: destroying vetted german infantry at large ranges. Infantry costs MP to replenish. Damaged tanks can be repaired for free, and a ISU will find it much more difficult to destroy anything above a p4 due to its slow reload(in comparison to a SU85). This is basic sh!t i can probably expect you to know, but i put it out here for those that don't.
In short, if you use the ISU152 for AT purposes you are not using it to its full potential.
this does not mean that is has horrible tank- versus- tank performance, as it does have the damage and pen to make german heavy tanks back off. But that is where it ends: it is only good at scaring them off, not killing them, because of the reload. If you want to kill tanks as soviets, you get an SU85 which has similiar pen.
I'm really going to leave it at that before the mods put a big, fat, thick, shiny lock on this thread for derailing.
(p.s.: if the ISU152 performance is so OP according to you, make a different thread about it. I'm certain we can keep this thread about Tiger1 as much as possible if people here are willing to)