It seems that Orc NPCs, Followers, and the like, do not have any form of regeneration. Any damage done to an orc is permanant.

In the CK, it says their Healrate is the default 0.7, but in game, their healrate is set to 0.00.

This is with No mods active, Just Skyrim and Update.

To test, load the game, do a coc markarthshrineoftalos. Exit and look down, the female Orc Smith should be there, do a getav healrate, and it will display the regeneration rate at 0.00

This makes orcs almost useless as followers.