I think fighting larger groups of enemies should be the natural progression of the combat system. You start out with 1 guy, early on, as you're learning the system. You grow, you gain new moves, feats, and tactics. The game gets a little easier, so now you might see 1-2 enemies come at you, trying various tactics against, training you to fight and kill more efficiently. Eventually, you grow again, you become more powerful. The game starts to get easier. So the evolution continues .... Now 3-4 enemies confront you from time to time, but they are still lower level than you.
A lot of your special moves can stun an opponent, or knock an opponent to the ground. In the time purchased by leveraging your more successful attacks (since the enemies are lower level than you, more of your attacks work against them to buy you time), you switch to another opponent, and do your best to weaken or find that precious moment when you can turn the tide of battle with one of your well-timed strikes.
Maybe then, in combat with multiple adversaries, you could gain some special moves that allow you to quickly switch opponents. Say you strike the blue warrior in front of you with a staggering blow, and instantly spin and strike the red warrior behind you as he closes in. You do a few strikes, gain a new special move, execute a staggering blow, and whirl back to the blue warrior again, keeping all of your enemies in the whirlwind of your battle frenzy.
As you gain more levels, say you're like 20th, now you can sometimes be surrounded by 6-10 warriors. You sweep your sword in an arc between forward strikes, pushing enemies moving in from behind back, you grab some enemies and throw them into the other ones, knocking down 2-3 of them. You throw a dagger at one enemy behind you, which strikes a nerve, causing them to writhe around in agony instead of trying to attack you. While these 3-4 enemies are wounded, you attack the ones that remain. One blow is so forceful you knock your enemy off the ground. He collapses on his back. You whirl and face the next one. He's tough, but you're faster. Your flurry of strikes knocks him senseless, and while he is recovering, you whirl and execute a killing strike (finishing move) on 1-2 enemies (decapitating two of them with one sweeping strike of your longblade. If you have a dagger, then no!) ...
Eventually, you can walk into a group of 25 enemies, shield bash them, sidestep them, trip them, throw them into each other, slide under them (toppling them), all the way levying cuts against them, where each strike you make is 80% of the time a killing strike. They are fighting a war of attrition against you, each one only able to get 1-2 strikes against you before you dispatch them. So that you know you are powerful because it takes a small army to fight you.
Not every battle, but once in a while, yes. There should always be awesome new powerful enemies to face 1 on 1.... but to leave out the opportunity to demonstrate your awesomeness in having worked your character up so high, it would be nice to see crowds of enemies confronting you in their futile hubris ...
... then and watch them die beneath your mighty blade ...