The ISU-152 requires a lot of support to function properly. Germans have, unlike the soviets, plenty of main battle tank options that can engage and circle an ISU-152 and take it out in a timely fashion. This is not only do to the germans superior penetration and dps values on their main battle tanks, but also due to the ISU-152s weak side/rear armor.
The elephant on the other hand is much more difficult to take out. The soviets main tank destroyer does not have a turret and is an easy target, and their main battle tank has low penetration and DPS. Even when flanked by a T34, the elephants thick armor and massive HP ensures that you have plenty of time to take out the T34 before the elephant goes down, even when caught unsupported.
I have never had a problem taking elephants out. If you are discussing a doctrinal unit as if every Ost player will deploy it I am going to say mark target and 1 T34, done.
Or if you can't do that try guards, or failing that, try shocks with a shrek when you find one. Or if all that fails get a zis. Or use kats to pick away at it. Or, and I cannot stress this enough, place mines as you retreat. You have the munitions. Elephant with engine damage is dead. You can bomb it, you can strafe it, you can hit it with arty, and it can't move. Keep in mind you can lose 3 t34's and come out ahead when fighting an elephant.
You can beat it using only 2 su85's, going shocks, and relying on other units to bring it down. It was easy to lure the elephant into a duel with 2 su85's and use mines and bombing runs with kats to whittle away at supporting units and it. Even better the player was desperate to repair the elephant so I would stop firing arty for long periods to encourage pioneers to approach and repair then hit it with a combined strike to bleed out man power. Eventually killed it with 1 su85 shot to the front when it was low health. In addition, I knew at all times where his entire army was located since he could not leave the elephant. Elephants are hard counters to soviet camping game play approach, but relatively weak to a mobile and aggressive soviet player.
This is not really a discussion about 152 and elephant. This is about Tiger and IS2. I really don't feel either the 152 or the elephant is not filling its role well.