Hoid is both an Allomancer and a Ferrochemist. But please note these few things about him.
1. He didn't necessarily use the bead of Lerasium to become a Allomancer unless there was an interview that I didn't read. Regardless of whether he is a Mistborn or just a Misting, and similarly with Ferruchemy. It's still possible that he is compounding much like the Lord Ruler did in order to stay young.
Brandon said "He did steal a bead of Lerasium off of Scadrial. If he were to make use of that bead, certain powers would have been gained."
2. He would likely be from Scadrial given he could gain BioChromatic Breath. Despite this many people think he is from Yolen. I will admit that I haven't read ever book in the Cosmere yet, but I'm almost done, and my theory makes sense; at least to me.
3. None of his powers are gained from Hemalurgy
So little is known about the ability LightWeaving on Yolen, so to assume that he's from there and that it is heredity it foolish, so let's assume that like BioChromatic Breath, LightWeaving can be gained, or like Forging, it can at least be taught.
The ability to visit Shadesmar can be gain in many ways, and the ability to manipulate it comes from practice.
He uses Feruchemy to gain limited foresight, so he can know where he should be.
This leads to my believing that he has lived through ages, maybe even since the shattering, though we know he isn't a Shard. It's quite possible though.
As far as we know, Ferruchemy is strictly genetic, but being the oldest form of magic on Scadrial, it makes sense that he is from there, likely before the Rise of the Lord Ruler.
His ability to heal and "bend time" could also come of Terris heritage.
I don't think that he is a MistBorn, but rather a twin born of multiple abilities. NOT a full MistBorn and Ferrochemist though.
Comment below with objections or support of this theory, I'd enjoy hearing what you guys think about it.
-Java