Every other U16 item has a clear niche in which it is either solid or it excels. Then along comes this piece of garbage.
+7, Cosmic, Greater Stone Prison, 2.5[1d8], DR bypass: Adamantine. Min level 25, epic elite version.
For comparison consider the EE version of the Forester's Brush Hook. Both require an exotic weapon feat, both have the same crit profile, both do effectively the same damage (Phlebotomizing and Cosmic are of about equal overall power). The Hook bypasses basically every DR in the game; this silly khopesh bypasses only a few. The Hook can be used in monk stances by some builds, this silly khopesh doesn't have that edge.
Especially given how popular khopeshes are and how many people are looking for named ones, this really could do with a boost. It doesn't need to be the best weapon in the game, but adding something like Annihilating or the force version of the tier 3 Alchemical AoE procs will make it genuinely worthy of consideration. Otherwise this unique-looking art will largely go to waste.