So assuming you max the appropriate skill (normal weapon skill or tenebrium skill), is it better in the end-game to:
1) Use a "true" tenebrium weapon
2) Use a crafted weapon with whetstone upgrade and +tenebrium damage (via applying a tenebrium bar)
3) Use a "found" weapon with elemental damage and +tenebrium damage (via applying a tenebrium bar)
?
depends on which kind of t weapons you come across is the most powerful by the end game.
I've heard people going 2) and create some very sick weapons. I myself, not into crafting weapons from scratch, just upgrade legendary weapons and then add Tenebrium enchantment.