There are no units in a "class of their own". Every single unit in the game has a counterpart on the opposite 'side' that is similar, if not identical, in role. It's 'power level' might be different, as could its cost, but there are counterparts.
ISU/JT/Ele
KV2/Brummbar
SturmTiger/AVRE
Tiger/Pershing/IS2/KT
STUG-E/M8A1 Scott
Further more, you completely missed:
See Vipper's post. The AT power, when using AP shells, its actually quite good. It's not as good as a JT/Ele, but that's because those two units can only deal with vehicles, whereas the ISU can actually do damage to infantry.
Let's compare the ISU and Ele, against the toughest non-doc targets they can face, and at max range.
At 70 range, the ISU has 200 pen, and deals 240dmg, with deflection 120dmg. It has an average RoF of 10.26s. The toughest non-doc Axis vehicle is the panther, with 260 armor and 960hp.
This gives it a 77% chance to pen (and deal 240dmg), and a 23% chance to bounce and still deal 120dmg. That means, on average, it deals (185+27.6) 212.6dmg per shot. That works out to 4.5 shots (i.e. 5) to destroy a panther, which means 4 reloads, meaning 41s on average.
At 70 range, the Ele has 360 pen, deals 300dmg, with 0 deflection damage. It has an RoF of 8.76s. The toughest non-doc Allied vehicle is the Churchill, with 240 armor and 1400hp.
This gives the ele a 100% chance to pen (and deal 300dmg). That works out to 4.66 shots (i.e 5) to destroy a Churchill, which means 4 reloads, meaning 35.04s.
41/35.04 = 17%
So the Elefant is 17% better than the ISU against the heaviest targets they can face.
Against mediums?
An M4A3 Sherman has 160 armor and 640hp. That gives the ele a 100% chance to pen, meaning 3 shots, or 2 reloads; so 17.52s.
An Ost P4 has 180 armor and 640hp. That gives the ISU a 100% chance to pen, meaning 3 shots, or 2 reloads; so 20.52s.
20.52/17.52 = 17%
So the Elefant is 17% better than the ISU against an average medium tank.
I'll trade that 17% AT power for the ability to 1-shot squads.
What kinda bias assed analysis is this? Using THE absolute most durable unit in the entire game as a baseline for one faction and not even the axos' most durable unit into account for the other? (the KT is the axis most durable stock unit) To give an accurate picture (which you clearly elected not to) one would use similar targets OR the high end for both factions. Ideally both. One might use the KT as an example counter to the churchill, not a Panther that has SIGNIFICANTLY less health (and still the elefant comes out 17% better? Dealing with an entire medium tank worth of health extra? Can you get more biased?)
Yoi neglected to include the elefant is GUARANTEED to deal more damage (more than 2x as much on an isu bounce) AND does it faster.
Against a medium tank both elefant and isu take 3 hits to kill, but the elefant does them quicker.
Against a premium medium (Panther, comet, t-34/85 ect) the isu needs 4shots or more as it's not guaranteed to pen
The elefant needs only 3 and is guaranteed to pen against all targets.
The fact that an elefant can kill a churchill faster than an isu can kill a Panther means an elefant could literally kill 2 tanks in the time it takes an isu to kill one. That's a fuck lot better than 17% and you damn well know it.