I've got an idea for how you might adjucate combat quickly. A combat situation might go as follows.

You (the GM) describe the situation just prior to combat, giving the player as much information as the character can see.

The player than chooses one of three basic stances: Aggressive, Normal or Cautious. An aggressive combatant throws themselves into battle with little thought of defense or escape. A cautious combatant moves carefully and is ready to flee if things go against them.

The advantages and disadvantages of the three stances are list below:

Aggressive: This is a brutal combat style, with maximum chance of death, and little chance of the other side escaping. If the PC is much stronger than his foes, he will quickly trounce them. If the the PC is a little stronger than he foes, he will beat them, but is likely to be injured himself. If the PC is a little weaker than his foes, he'll be soundly beaten. If the PC is much weaker than his foes, he'll almost certainly die.

Cautious: The PC errs on the side of safety. He is less likely to die, but his enemies might escape him as well. If the PC is much stronger that his foes, he will trounce them. If there are a lot of them though, some will escape. If the PC is a little stronger, he'll win, but his foes will probably escape. If the PC is a little weaker, he'll lose, but will probably be able to escape. If the PC is much weaker, he'll lose, and probably won't escape.

If the PC chooses normal combat, it will run like an agressive or cautious combat depending on what attitude the NPC's take. Basically, if one side is aggressive or passive, the entire combat counts as agressive or passive. If both sides act normally, or choose opposite stances, it's up to the GM (though I personally would err on the side of PC survival).

Aside from the basic stance, the PC should give a combat plan: how they plan to go about attacking the NPC's, what powers they are using, etc, with a couple of contingencies for possible NPC reactions.

To resolve the combat, the GM should compare the PC strength to the NPC strength, taking into account how clever the PC's combat plan is. She should resolve it into one of four categories: PC is much stronger, a little stronger, a little weaker or much weaker.

If the PC is much stronger, they will certainly win. If the PC is much weaker, they will certainly lose. Whether or not they were aggressive or cautious doesn't make much difference.

If the PC is a little stronger, they will win. If they are aggressive, the NPC will get in a few licks before they die. If they are cautious, the NPC's will probably get away.

If the PC is a little weaker, they will lose. If they are aggressive, they do some damage before they go down. If they were cautious, they can probably escape from battle, though probably with a few injuries.

Basically, if the PC thinks he's stronger, he should be aggressive, so his opponents don't get away. If he's thinks he's weaker, he should be cautious so he can get away. A good plan can push things in his favor, while a poor plan (or no plan at all) can push things against him.

Note: The question of combat never arose in my game, so this system is untested. However, it does seem to be the best way of handling things, bearing in mind that it would be pretty much impossible to do a round by round combat, especially in a situation where only some of the players are involved.