The Sun King said:
Ghouls and GG hordes will absolutely slaughter it.
I doubt that. Let's do the math on it:
Frostheart Phoenix vs. 40 Ghouls:
Frostheart Phoenix charges (orders of magnitude more mobile). We'll assume +1I on Attuned to Magic, to not swing things in any significant way.
Frostheart Phoenix strikes first. 4 attacks, hitting on 3+, wounding on 2+, allowing no saves.
Math: (4)*(2/3)*(5/6) = 2.22 Wounds
Thunderstomps strike tied for second. D6 autohits, wounding on 2+, allowing no saves.
Math: (7/2)*(5/6) = 2.92 Wounds
Ghouls strike tied for second. 16 attacks, hitting on 4+ (autowounding on 6s), wounding on 6s, allowing 5+ armor, 5+ Ward.
Math: (16)*([1/3]*[1/6] + [1/6])*(2/3)*(2/3) = 1.58 Wounds
HE Wounds: 2.22 + 2.92 = 5.14 ~ 5 Wounds (35 Ghouls remain)
VC Wounds: 1.58 ~ 2 Wounds (Phoenix has 3 Wounds left)
HE CR: +5 Wounds +1 charge = +6
VC CR: +2 Wounds +3 ranks = +5
HE win by 1,
VC crumble by 1 (34 Ghouls remain).
As you can imagine, if the fight remains in a holding pattern, the Ghouls will probably grind the Phoenix down across the course of 3-4 rounds, which is not the worst result out there (staggeringly unlikely to happen, though, as no HE player will charge a Phoenix into a Ghoul
Horde alone, and you're not catching it with M4 Ghouls). Let's check out how Grave Guard fare:
Frostheart Phoenix vs. 40 Grave Guard, Full Command, Banner of the Barrows:
Frostheart Phoenix charges (orders of magnitude more mobile). We'll assume +1I on Attuned to Magic, to not swing things in any significant way.
Frostheart Phoenix strikes first. 4 attacks, hitting on 3+, wounding on 2+, allowing no saves.
Math: (4)*(2/3)*(5/6) = 2.22 Wounds
Thunderstomps strike tied for second. D6 autohits, wounding on 2+, allowing no saves.
Math: (7/2)*(5/6) = 2.92 Wounds
Grave Guard strike tied for second. 12 attacks, hitting on 3+, wounding on 5+, allowing 5+ Ward.
Math: (12)*(2/3)*(1/3)*(2/3) = 1.78 Wounds
HE Wounds: 2.22 + 2.92 = 5.14 ~ 5 Wounds (35 Grave Guard remain)
VC Wounds: 1.78 ~ 2 Wounds (Phoenix has 3 Wounds left)
HE CR: +5 Wounds +1 charge = +6
VC CR: +2 Wounds +3 ranks +1 banner = +6
VC win by 1 (Musician).
As could have been perhaps surmised at the start, the Grave Guard fare a bit better against it, though that should be expected of a unit that clocks in at more than twice the price of the Phoenix itself. Either way, I wouldn't call that a "slaughter", or anything close to it. Gheist or Snipe them off the board, 'cause your infantry won't do a good enough job of it, especially when you consider they'll be getting laid into by a High Elf block at the same time.