Boy, this is a tough one to crack, mainly due to the way these units perform across modes.
Some people on the balance team are advocating for final tier side tech as a more equitable solution than tying heavies to all tech buildings etc.
Do people like this proposal?
Also, what (if any) further nerfs do people think would be needed in conjunction with the above?
A separate tech is the simplest way to adjust timing and tech cost for these units but that is not the only issue. These unit are simply way too cost efficient.
Currently a Tiger can replace a both a Brumbar and Panther.
And on the other hand some of the TD ignore the armor of these vehicles.
Possible way of fixing some of the problem.
1) Lower the price and Power level of these unit. For instance Tiger could become a Super Comet and IS-2 a Super Churchill
2) Lower the performance in one area so that these unit require additional support like the Tiger could be better at AT and the IS-2 better at AI.
3)Lower base stat so that the shock value of these unit would go down and increase the vet bonuses so that they become rewarding once vetted.
4) Lower cheesy counter like Ram+of map
Finally one has to keep in mind that the performance of these units is tied to their counters so balancing them should go hand in hand with balancing heavy TDs.