How about giving a Tiger it's stripes?

[Tomalak]

I find it interesting you didn't find the Tiger strong enough, I was very pleased with its performance. For example, in bonus mission The battle of Vernon, a single Tiger can hold the entire middle defense. Or the final mission in the Allies campaign. The Tiger in the last German mission gets a lot of punishment from different sides, and at low ranges, increasing the chance one of enemy shots will penetrate the armor, especially having in mind that multiple hits to the same spot can weaken the armor.

The problem with modeling Tiger's (and other heavy tanks') strengths in games are ranges. A big part of its power comes from ability to engage targets at huge ranges, at which his own armor is impenetrable. Its 88mm KwK36 L/56 gun is rated as able to penetrate a 100mm tick homogeneous armor plate, at 30 percent from vertical angle, firing from 1000m (84mm from higher range of 2000m).

So the main challenge of an opposing tank is how to get near enough to a Tiger for its own gun to have any chance of penetrating Tiger's armor, without being destroyed.

Since the games usually don't try to represent these kinds of huge ranges, tanks like Tiger (as well as high caliber guns) lose a big part of its advantage.

At low ranges, like 100m and below, the situation changes significantly.

So the real challenge for developers is how to balance more powerful tanks properly. If you try to compensate for inability to represent huge firing ranges in a game by making a tank too powerful even at shorter ranges, you will have balance problems, because it will be invincible to anything except similarly armed tanks. You can see in mentioned missions (Vernon and last Allied) how Tiger's survivability increases significantly if engaged in duels at its maximum effective range, and in these conditions it can really take a lot of punishment. This, however, also means that its survivability decreases significantly as range does, since the maximum ranges in the game are not that great to begin with.

EDIT: Another interesting example is the British Matilda (II) tank. With its armor value which was higher then most other vehicles at that moment, the only thing that could knock them out in the desert (before more powerful tanks entered the theater) at respectable range was the 88 Flak. Its other disadvantages, like low speed, are not really relevant in most games, since game maps are not big enough for any serious maneuvering. But if you tried to represent this (armor advantage) even at (low) game ranges, you will produce a big balance issue, since many gamers (and you can't target only hard core WWII fanatics) will have problems if at the beginning of their campaigns they start facing "little invincible British tanks".

The mentioned 88 is at a big disadvantage in games too. Similar to Tiger's problem, once the enemy tank is in range, it doesn't take long until the 88 is under fire as well. Difference being the gun crew doesn't even have comparable armor protection.