As it looks now, damage UVs are considered pretty worthless. I'm not saying my idea would make them as desireable as ASI or CTR, but I believe it would be pretty nice if damage UVs would affect two kinds of enemies, divided by the damage types they inflict. Undead and Fiend UVs would be converted into a single type of UV which has effect against both enemies, same for Gremlins/Constructs and Beasts/Slimes.
This could also be applied to some gear and weapons with inherent damage bonuses against monster families, such as Deadshot, Cold Iron Vanquisher, etc. Perhaps not all of them, though.