Yeah, the idea of having a dueling weapon against heavy armored foes, mindless beast, creature as large as a barn is laughable. I did a lot of fencing once and I can tell you that the main reasoning behind the finess weapon being able to to as much damage as a heavier weapon against an armored adversary; that your PC hits between the plates, is strange. There's no way a fighter with a rapier is able to pinpoint 4 times in 6 seconds the small breach in the armor while the foe is defending himself.
Anyway, in my head canon Scimitars are Sabers and Rapiers are Broadswords, longswords are Arming sword, two-handed swords are Longsword.