My solution would be to introduce a joint cooldown on all abilities that become OP when they overlap. It would be better than nerfing them, as then they may become completely useless. For example, I would make sure that once mark target is used, a player cannot use ram or off map stafes (maybe all, or just some of them), until mark target finishes. Such cooldown could be set to regulate the cheese between some/all abilities. It only should only be decided which abiities would be mutually exclusive.
Miracle idea...
Some of best combos:
1. Stun shot + AT stuka
2. AI strafe + cluster bombs
3. Combined arms + rangers with zooks
4. Ram + AT artillery (from defend and nkvd commander), much easier to exploit than il-2 bombs and il2 rockets
And it's only 1vs1 combos, in 2vs2 this list will be much longer.