Biggest problem is the HE AOE of the ISU to kill infantry.
From a stats on paper perspective - ISU and elephant toe to toe is a pretty even matchup
-Same range
-Similar damage
-Elephant has more armor, and a little faster reload
I like the idea of a switchable ammo option for ISU, perhaps both units. Thats what they did in real battles. Load an HE round, Load an AP round, etc. Then again we aren't exactly playing a real combat sim either lol.
I don't know what stats you are reading, but the ISU and Elephant do not go toe to toe. At all, the ISU is a lot weaker vs tanks.
- Range = same
- Damage = higher for Elephant: 320 vs 240. It's the difference between killing a medium tank in 2 hits vs 3 hits, killing light tanks in 1 hit vs 2 hits. And heavy tanks 3/4 hits vs 4/5 hits.
- Penetration = better for Elephant. At max range, only the IS-2 has a ~5% chance to deflect. It will penetrate any other enemy tank even at max range. The ISU only has 200 pen at long range, giving it only 50% chance to pen a elephant from the front.
- Armor = again, better for elephant. 400 vs 310 from the front.
The anti-infantry power of the ISU is there because the ISU is significantly weaker vs tanks than the elephant.
Now, I do feel the Elephant needs some love, but you made it sound like the ISU was an elephant + massive infantry killing power. Because it's not.
I would personally suggest giving the elephant some of his range back. Probably at least 85 just like the Jagdtiger.