It really is fine. Actually regular weapons are still more powerful than tenebrium in many cases, especially because you can craft them, so they can be :-
- sharpened for lots of extra damage
- added tenebrium damage by adding a bar to them
Okay, stop. When you add tenebrium to a regular weapon, that makes it a Tenebrium weapon. So when you add a T bar to your 2-handed sword, your 2-handed skill no longer improves your damage with it.