Agreed. a Rune Blade without SSI isn't worth much. 2.5 seconds per swing is too slow. Since the other mods are pretty darn good, you might get a few thousand gold for it, but don't expect much. With Disarm as its primary special, it's really only a PvP weapon (monsters don't carry weapons, so they can't be disarmed), and few PvPers want slow weapons.
Any weapon below 1.25 seconds per swing at 150 Stamina loses alot a value. There are a few exceptions where the dps (Damage Per Second) is still pretty high, but there aren't very many.