After going through the Dark Hunters book myself for the first time, I realized that there is one, or rather eight, Dark Hunters whose fate we do not know. The Hordika Dragons.
They used to be regular hunters, but the Shadowed One mutated them with Visorak venom and turned them into essentially supercharged attack dogs.
But did Mata Nui’s healing wave cure them? I checked the wiki, and there is no indication that they were or weren’t cured, or even if they are still with the Shadowed One.
For all we know, all 8 of them could be roaming as beasts, or they could be back to normal, and likely plotting revenge on the Shadowed One.
While it doesn’t say explicitly, the fact that most all other known mutations that were undone by Mata Nui were pit mutagen based/aquatic-to-amphibious transformations, and that they are explicitly stated to be reversed seems to indicate the Hordika Dragons’ mutations are not reversed.
There’s also this snip of text from BS01 on the effects of the Hordika Venom, “During its early stages, the transformation can be halted and reversed by those with a knowledge of how to cure it. However, past a certain threshold, the victim will inevitably become a Rahi.” Like others who are also long-term victims of the venom (Savage most notably), they likely are permanently mutated.
An exception could be made for other paths of undoing the effects. Again, quoting BS01 on Hordika Venom: " it is possible that a being wearing a Mask of Mutation, for example Makuta Miserix, could undo the mutations caused by the venom, but the user would need to know how it works. The Kanohi Ignika can also cure the effects by devolving the afflicted being."
Here it is mentioned that the Ignika could undo the effects, but that it would be by devolving the being. As Mata Nui was more revitalizing the life of the planet rather than devolving it (and would not be focused on the few with this mutation), again it is not likely that this was the case of action; even the pit mutagen cure was likely a side effect more than a directly targeted heal.
However, possibly Miserix could have a hand in their cure as a future plot point, somehow. We could have fun with that thought.
I’m not sure but I could have sworn that it was said (likely in a Greg quote) that Mata Nui only reversed mutations that were caused by or because of the Great Cataclysm, hence why it was mostly Pit mutations since the Pit mutagen was only created due to the Cataclysm. Hence, any other mutations such as Visorak mutations wouldn’t be undone. I could be wrong though.
So that implies that Mata Nui’s healing wave interacts with the inward desires of the MU inhabitants in some way. I imagine that if that were true, then the Hordika Dragons would be cured, since Mata Nui is using the power of the Ignika to do all of this.
It is true. So what we know is that 1. the life wave could undo mutations regardless of their origin (makes sense since it devolves beings), 2. it took desires of the individuals into account.
From this we can conclude that anybody that had conscious desire to be healed of some mutation that happened to them has been restored to their previous form: