Good news. The wedge is pretty good for smashing through.

I pierced through DFK four rows deep with a unit of basic feudal knights (no upgrades, no exp). I made them charge in wedge formation and double-clicked beyond the enemy unit instantly on impact.

Doing this five times my losses were 3 times 2 knights and twice 0. The losses all occured on impact. While moving through, my knights killed all enemies in their way and left a nice breach to be exploited.

It seems the enemy simply could not focus on a target, that's why I had no losses.

Quand meme I would prefer a formed standard attack. It's in most cases enough to cause an instant rout.