combat rating on item?

what it clearly means?
i've seen same umc part with different ms and they have different combat rating points
higher combat rating means higher damage?

 

Ye, but as for now in 6.0 these values are gone. Items shouldn't display it.

 

combat rating stats on 6.0+ is useless or just a numbers now?

 

Enchanting your armor/access/weapon and socketing manastone, will increase the combat rating value. You dont have to be a genius to understand that an enchanted item (enchant after enchant till the max) with manastones has better stats...this Combat Rating value was something which lasted from 5.6 to 5.8, then removed in 6.0+. Nothing special at all.