I would actually argue that all three are very good in minions. Void for obvious reasons, Primal is nearly a warbeast and has AOE 4 auto knockdown on all 3 attacks as well as being an amazing contesting piece, and Dhunian is a lifesaver in WWFF because it can take d3 damage to save lessers or contesting pieces. Also, the worst of these, the Dhunian, is probably going to get buffed because consensus seems to be that it's not that impressive.
Yeah, the Dhunian is going to need to get something extra before I'll consider her. I've been playing a lot with the lessers lately, and even without the many additional defensive benefits from Sturm, Dahlia, Brun, and Mire are all very hard to kill on their own. I can count on one hand the number of times I've lost of any of them before their respective Warbeasts. Generally, if they die, it's something that could have been prevented with better play on the Minion player's part. I can see her value with Wrongeye though. He's usually reasonably safe camping zero, but he's the most susceptible to random luck on your opponent's side so having some insurance against that would be valuable.
But until she gets a look over, I'd rather have a Mist Speaker. Clouds and Magic Weapons are more important more often than my experience suggests her Martyrdom would be.
I doubt they are going to let 4 of them be brought for free in WWFF (which is possible as it currently stands)
It might not be all that crazy to leave them as free options in WWFF.
I mean yes you can get up to 34 free points as is which is a bit ridiculous, but I think most lists would rather take some of our other support solos (soul slave, witch doctor, mist speaker, etc.) instead to function "optimally". Alternatively, you can build a list with 3 free cards in mind and put in 3 archons there. That still leaves you around 25-30 points to spend on valks or solos. Maybe I'm wrong, but it doesn't seem broken to me, it just gives us more (stronger?) options.
That said, we're still early in this CID cycle, but so far the Void Archon definitely feels like the most interesting for minions. Entropic Force and Dark Shroud are just always good, relatively easy to trigger abilities. I think Helga in particular loves the Voids most of all, there's just so much synergy between them. Dash with flying models is amazing, plus they're probably the best models to trigger gang fighter now, while also having amazing mobility to trigger a weird feat slam.
The Dhunian Archon is a bit underwhelming compared to the others, but the threads of life part can be really clutch for us. Either for keeping lesser warlocks alive or even other archons.
The Primal Archon is just a solid standalone model and a great scenario piece as is. Could be interesting with Maelok or Sturm&Drang for the extra armor and control?
The primal's ability to shut down placing should not be ignored. It solves some major issues, such as LotF, TK, recursion, etc, and is a potent contesting piece being arm 18, 12 boxes and sturdy, plus countercharges to get it into a zone if needed.
Honestly the only thing on the primal that disappoints me is hyper regeneration, and that's just because it likely won't be relevant. I don't know if rapid healing would be too strong on it, but probably.
I think the Archons would all generally need some buffs before I think they can be considered busted as free solos. We've got Lord of the Feast floating out there outperforming all of them on both resilience and potential output (yes, FA2 versus C changes things a little, but not enough to make up the difference), and outside of Void the tech the others bring along is pretty niche. They're just... not really worth their fairly significant price points as things stand.
As long as they are free in theme their cost is 0. You'll just pay 4-5 for the other solo instead.
That is my point. Currently, they're not notably more impactful than critical tech pieces we already have in Minions (i.e. the Mist Speaker for Guidance, Orin Midwinter for spell denial, and the Soul Slave for massive Fury dividends on your Warlock), and as combat solos they don't meaningfully outstrip the Lord of the Feast, to take the most obvious example. Unless Archons across the board get a bit of beefing up, I don't think they're that big a deal as free solos because for all their points they're still in meaningful competition against 4-5 point solos for those slots. I think I'd consider swapping out my Mist Speaker in my Sturm and Drang list for a Void Archon, for example, but it's an extremely tough call and I don't think there necessarily is a "correct" answer on which version is the most effective. Certainly, the Void wouldn't replace Orin, Eilish, or the Soul Slave in that list, they're all too integral to how it works. Similarly, in my existing Arkadius list, I'd almost certainly slot one Void Archon in, and maybe two, but I wouldn't touch the Primal or Dhunian ones in spite of the fact that I'd get double the free points swapping out Targ or the Witch Doctor for them. They're definitely up there as free point solos, and it would probably be rare to not have one free Archon in a list, but as per Week One rules there's not much to be gained from loading up on them.
That said, we'll likely see changes to the Archons in the coming weeks, and if they get stronger across the board in the coming weeks then my position will certainly change.
On the flipside, the change removed Efaarit Scouts from Thornfall... but added the Dhunian Archon as a free model choice? And she's still available for free in WWFF. So definitely the one to keep a close eye on.