In 2v2, the maps are small enough that if a player gets a successful ram off on an OKW heavy tank, the heavy is guaranteed to get hit by either IL-20 or Rocket Strafe. The OKW heavies simply don't have the movement speed to escape in time on most 2v2 maps, which are small enough that a plane + ram is a guaranteed combo.
There is no counterplay other than to try and avoid the ram. Given how easy it is to get a ram off, I think this combo is absurd in 2v2 personally. It basically makes OKW heavy tanks completely useless in 2v2 other than for the Tiger, because the Tiger actually has the acceleration and speed to escape the off-map once it gets rammed. It also completely negates the OKW heavy tank's role as the centerpiece of a push.
Curiously, this isn't a problem in 3v3 and 4v4 as the maps in these game modes are generally big enough that a the plane takes too long to reach the tank, and the heavy tank can escape in time (at least, the King Tiger generally can; the Jagdtiger is so slow it tends to get hit anyway).
Yes, I agree with you. As I commented before:
In general, "1-click" counters need to be removed. Ram+Off map, like any other "1-click" combo, is OP by any definition; once clicked, there's no counter. The targeted vehicle will take massive amounts of damage - often enough to destroy a 720mp/260f/15 point vehicle.
Anything that powerful needs to have counter-play available AFTER the attacker has "clicked". In most situations, powerful abilities/combos like this have counter-play options - this is one of the few exceptions. The problem is, it's the combination of two abilities that makes it so devastating; so we're left in a situation where one needs to be nerfed a disproportionate amount in relation to its individual power.
My preference would be a ram nerf, as the off-map is currently in-line with similar abilities. Ram should likely be adjusted to have either much less range, be a "skill-shot" (i.e. straight line), or (as suggested by Stormjager) have different effects based on the targets remaining HP.