tl;dr:
The main thing I noticed when using it was the passive was extremely difficult to activate for the player unless you resorted to hiding your army or keeping it stationary to allow missile units to hit you. This essentially made your army immune to missile damage, while providing a map wide heal.


I think MoF should be strong for the AI, but from my experience it doesn't end up working out that well in battle situations. I typically end up bursting it down because it dives in before their army is engaged. It was easy to remove from combat.

As the player the unit is/was too strong. The speed on it allows it to single handedly dodge an entire army or two worth of missile units. It's almost as if the AI can't predict movement with that amount of speed. And if you're trying to activate the passive you intentionally needed to take massive damage on it before the fighting begins, so you can avoid losing models in your armies and maximize the benefit of the passive. The severity of this means I was able to take an entire SoA stack(rank 3 and no research buffs), put them on melee, get the passive heal activated, remove the pheonix from combat and then win the battle without any unit loses by just using sistsers in melee. I put them in a locked formation, charged in, and only selected new targets to allow them to pick their own fights.

An option to balance the massive healing is to make the passive only activate when in melee and above 10-25% hp. Otherwise you can dive it into an unfavorable match up and benefit from it because it ultimately doesn't have any bad match ups. I very much like the idea of map wide healing, but not on a unit that's stronger than most lords. It doesn't win everything, but it literally has no counter that can remove it from the battle field if you put any effort into positioning it.
Maybe even something where it has good combat stats, but upon taking too much damage it "transforms" into a defensive healer at the cost of damage stats. Maybe a boost in melee D, massive nerf to attack skill That would force the player into a trade off decision and also make the AI readjust it's combat priorities?

on a side note; I couldn't find a use or point to adding any of the other units to a roster in my campaign. By the time I conquered the territory the units gained would underperform what i already had fielded.

Caledorian Honour Guard:
shares weapon strength of swordmaster
shares research from phoenix guards
Interesting unit, but replacing them on a 3 turn recruit wasn't viable. The added cost and recruit time didn't suit my style play. The main drawback was melee units typically need to be replenished after hectic battles(I intentionally skip lightning strike), so the 3 turn global recruit made them impractical for the way I play. Pretty good unit overall though


Asrai Spearmen
&
Eonir Stag Riders:
By the time you gain that settlement the units aren't practical; no added value to the army, but the building buffs were nice.

Free Company Militia
&
The Seafarers:
too late in the campaign to field these units. standard tier 1 archers shred them.

Still would be nice to test it manually, because its hard to predict how good or bad will be those units with new stats while it's on the "paper".

About MoF Regeneration ability.
In my opinion presently this ability is totaly fine, but I would change PHYSICAL resistance to FIRE resistance, just because the description says: It protects from flames.

Glad you listen your users ;)