Let me get this straight. late game there are weapons which are superior but can only be used with tenebrium skill. So all the points you put in to your normal weapon skills become useless. Seriously who is the person that designed this? How does crap like this happen?
Tenebrium skill could perhaps have a prerequisite of 5 in a main weapon skill. You could then only use tenebrium weapons which match your chosen weapon skill. Ranking up tenebrium would apply a small damage bonus perhaps? 5% 5% 5% etc. Maybe this would contribute too much to the damage snowball effect late game.
Perhaps the Tenebrium requirement on the weapon should subtract from the normal weapon skill (representing the difficulty in handling a Tenebrium weapon safely), and each point in the Tenbrium skill offsets that penalty.
i.e. a tenebrium requirement of 3 on a two-handed sword applies a -3 to the users two-handed weapon skill, but can be lowered to a penalty of -1 to the two-handed weapon skill if the user had a tenebrium skill of 2.
+ or - what? AP? This could work and end game damage wouldn't snowball with more damage bonuses. I haven't made it to end game yet but have read it gets easy, even on hard. Perhaps combine your suggestion with mine, a primary weapon skill prerequisite of 5 and only use tenebrium weapons of your chosen weapon skill. I like it.
I'm beginning to wonder if I should pursue my current save or wait for another patch or two.