[ano]

Yes, Machaka is the fetish king race Not using fetishes with them is unwise and maybe that's one of the reasons it is considered so weak - people just don't like fetishes.
There're several others though - namely EA Ermor, Yomi, Oceania, Ulm, EA and MA Tien Chi, LA Jomon. Of these MA TC and EA Ermor have access to good healers which should (as I mentioned) be a strong argument to think of fetishes.

As for the sorcerers/sorceresses - they share the same mechanics - when they lose last HP they shapeshift and come with full health next turn and have a chance to heal afflictions in process. There's one downside though - when they come with full health they have a lesser chance to bring a gem.
Any commanders with second form will behave in the same way but nations that can recruit them don't have native access to fetishes.

p.s. As for Colossal Fetish, I don't think it is a good pretender. It is too vulnerable because it can't retreat unless it is given Astral.