Well then.

In real life someone with a dagger is not going to face someone with a Sword, height is a person with just a Sword going to face a person with just a dagger. Adding to that, duel wielding really is a piece of fantasy. No one is going to wield two weapons because of the confusion it will bring. Fighting with a sword/dagger alone is already about knowing where the edge and point of the blade is while also knowing where the hilt and crossguards are. Adding a second thing with all of that is just going to take what is already difficult and times it by 2. It we are talking longswords, no one wielded those in a fight without a shield. We often like to think of Longswords clashing together in battle, edge on edge but in truth they didn't do that. Infact that was the quickest way to blunt your blades or chip them, which is much worse. They would use the flat of the blade to knock other weapons away rather then the edge.

Knights and anyone using a Longsword must use a shield because it balances it out. The Longsword is the offense because it offers no real defense. The shield on the other hand is the defense because it offers no real offense. Daggers came in when the duel gets near the ppint of exhaustion, which would be within 5 minutes. If the person they are fighting isnt important enough or too much of a threat they would bring out their dagger. They would already be too close from the start of the fight for the Longsword to really come into effect. But one of the fighters would bring out the Dagger and go for the gaps in the armour, usually into the armpit, the inside of the elbow, the gap between the helmet and the pauldrons and upper armour and the eye slits. Ignoring the inside of the elbow, all of those are lethal

See real life fights like those between people with longswords are never going to be the fantasy stuff we always seen in movies, games, shows or read about in books. You would close the distance asap to prevent your opponent from using their reach. Swords are heavy and stopping a swingthrough isn't as easy as we like to think. The weight carries, another reason a shield was necessary.

More often then not though the armour would come into play. Warriors would get tired quite quickly. Prolonged fights would see both combatants down within 10 minutes, depending on the armour they wore.