Maybe an automatic mechanic could be implemented, I am thinking of boardgames that use such a mechanic, f.e. KingdomDeathMonster, or D&D4s MonsterManual1 that had suggestions which combinations of powers worked best.
Example:
Orcs are wild, reckless fighters, that will always use Chop&Chop or slash&thrust, never defending themselves.
Kobolds are sneaky, cowardly fighters and will use thrust&defend or dodge&thrust with spears or daggers&shields.
Clever players(or characters with the right use of skill/talent) could learn, which tactics are implemented by a type of enemy/monster and plan their HiddenCombo accordingly.The GM just has to choose between two given options. This could speed up Hidden Combo Combat, if it is available all the time. In KD:Monster, monsters have a deck of options, which are at the same time their hitpoints, reducing their choices over time. This could also be implemented in a D&D4 UNbloodied/bloodied tactic. As long as a monster is above 50% health it uses Combo A, when it drops below 50% health it uses Combo B...
I still think, given the information we have for now, that using HiddenCombo just for duels or special "boss"fights will work better.