The Tiger itself is a bit under performing than what it's supposed to be two Su85s can take it out easily and one unlucky mine, at nade or ram will make it vulnerable to even one su85.
The tiger underperforms? And your reasoning is that it's because it loses to tank-destroyers? Two SU85s are more expensive than a tiger, and are dedicated tank destroyers. I would be a bit silly to have a tank destroyer that loses cost for cost against a all-purpose main battle tank in a straight up fight.
Here is a list of units that counter a tiger: SU-85 and Zis3 guns.
That's it, all other soviet units lose to tigers cost for cost.
Also, with a mine/pfaust, a IS-2 also loses to a single STUGIII or panther. This does not mean that the IS-2 underperforms. It means that mines/ATnades/Pfaust/etc do their job.
Instead of it being a good heavy tank it's too expendable and too weak. Relic needs to make it perform better and make it more expensive.
I would rather not have a unit that is good regardless of circumstances. If you want to counter tank destroyers, get a elephant, panther, or panzerschreks. For all else there is the tiger.