No, I think you are spot on. To say it bluntly: Swords suck.
In addition to your good summary, swords also require both DEX and STR to be effective, while knife/fists need mainly DEX, and sledge need mainly STR.
If you want to use Ripper you even need a bit of WIL. If you want some mobility and staying power, perhaps some crafting too... you need ability points all over the place.
The RNG part of Flurry/Onslaught is particularly annoying, unless you don't have a problem with savescumming. Personally, that is not the way I play games, so no Flurry for me, thank you.
The only interesting thing about swords is that they are one-handed, so you can use them with a shield. Can't see how to make it efficient compared to other melee, though.