So some personal testing with that 29 hunter I been screwing around with... seems to be much more important to be an epic item than rare with proper stats, as in mastery. Using rare items with mastery to replace epic armor slots without mastery on them basically resulted in a net loss of damage. Hunter-specific, not sure about other classes... not gonna farm a ton more crap at 29.
Just common sense stuff, but verifying it for myself. Speaking of, also might be an issue with belt buckles, socketed a belt prior to copying a character over and forgot to gem it.... could not gem it after. Just said "enchanted: socket belt" on the belt with no socket to gem. Gear is too high after so dont forget, lol. Gems socketed before copy showed up fine.