Having to rely on one doctrinal unit to fight one unit is bad game design. When the Tiger ace was the king of coh2 Soviet players obviously saw the design flaw. Now Sov players have a Tiger Ace that can one/2 shot everything and shoots at arty range and everything is ok? This thing has range, armor and punch vs everything. In order to get close to it, you have to kill the rest of the sov army while getting pummeled by it's cannon. This thing now has no weaknesses and thats a really bad design.
ISU has no weaknesses? Hmmm slow rotate, rear armor?
So what weaknesses has Tigers Ace? Great armor, great AT, not bad AI, speed etc. Only range.
Elephant - best AT, insane frontal armor, penetration, damage. Only bad AI. Combain with Brrumbar and you will recive very mobile short-range 'ISU" + Long-range best AT.