I dislike that having 0 skill in (example) two-handed weapons and 2 points in Tenebrium handling should makes someone a better two-handed tenebrium swordsman than someone with a maxed two-handed weapon skill and 1 point in Tenebrium handling.
Nailed it, i think Tenebrium at least should be treated as a weapon enhancement/enchant including it's current penalties if you are not efficient (skilled) with it; and with the current implementation that overlaps a skill that some people has invested a lot of points into it, it just feels clumsy and a bad implementation of a game changing mechanic.