I am talking about teamgames, I dont know how it scales in 1v1 games.
atm in 2v2s the ISU is almost unbeatable in certain situations and maps. americans spam vet rifles and get bars/zookas + fuel caches, while soviets go snipers/scout car or maxims and at guns, whatever they choose. even if map control is even, you're winning because youre saving all your fuel for ez8s and isu152s. once they come out it is very very very easy to just park yourself at a VP and take back any territories you lost during the mid game. since the american did not spend any fuel other than weapon unlocks, you can spam ez8s, while the soviet player just backs up the isu152 with snipers and guards. its rather bullshit and extremely difficult to fight against.
you talk about using combined arms to defeat isu152s, but you also have to remember that the soviet player will also be using combined arms to defend the isu, not to mention that their ally will trying to be covering for their weakness.
it was a fairly close game and we were even losing, but ez8s and isu152s come out and its just easy going from there.
edit: its not the best game to really show how stupid the ISU is, but its the only game i have on hand atm.