@Endzeitgeist - Enjoy, and try to ignore any egregious mistakes I made.
On reflection, I had actually later given the Grave Knight a customized +1 shield, so his total AC should actually have been 31.
The fight took place in close quarters, with the party pretty much all clustered by the doorway, which prevented them from immediately mobbing the pair. With the Grave Knight up in their faces, they forgot about the Grave Guardian. With his high AC, the Grave Knight was virtually un-hittable. The Inquisitor actually managed to buff himself enough to actually pose some semblance of a threat to the Grave Knight, but that DR 5/magic and slashing was a pain. Ultimately, the battle was won when, the Fighter and Inquisitor both nearly dead, the Alchemist remembered that he had ACID bombs in addition to his fire ones. They fell quickly after that.
GRAVE KNIGHT CR 3
NE medium undead (augmented humanoid) juju zombie knight 1/gladiator 2; Init +6
DEFENCE
AC 26, touch 12, flat-footed 24 (+9 armour, +2 shield, +3 natural, +1 Dex, +1 Dodge)
AC 30 with soft cover
hp 37 (1d10 + 2d12 + 9 + 3 + 2)
Fort +7, Ref +2, Will +1
Defensive Abilities channel resistance +4
DR 5/magic and slashing; Immune cold, electricity, magic missile, undead traits; Resist fire 10
OFFENSE
Speed 20ft.
Melee mwk longsword +9 (1d8+4/19-20)
Honourable Might mwk longsword +11 (1d8+6/19-20)
Or mwk longsword +7 (1d8+4/19-20) and mwk shield +6 (1d8+4)
Honourable Might or mwk longsword +9 (1d8+6/19-20) and Tusked Shield +8 (1d8+3)
Special Abilities Resplendent Power: 9 rounds/day
Honourable Might: gain +4 morale bonus to Strength
STATISTICS
Str 19, Dex 15, Con ---, Int 10, Wis 12, Cha 16
Base Atk +3; CMB +7; CMD 19
Feats Weapon Focus (longsword), Extra Resplendence, Dodge, Combat Expertise, Two-Weapon Fighting, Improved Shield Bash, Improved Initiative, Toughness
SQ Quality
EQUIPMENT
Other Gear: plate mail, mwk heavy steel shield, mwk longsword
And to make things worse:
GRAVE GUARDIAN CR 2
NE medium undead (augmented humanoid) juju zombie armiger 2; Init +6
DEFENCE
AC 24, touch 13, flat-footed 21 (+2 Dex, +1 dodge, +6 armour, +2 shield, +3 natural)
hp 21 (2d12+2)
Fort +4, Ref +2, Will +3; reflect
Defensive Abilities channel resistance +4
DR 5/magic and slashing; Immune cold, electricity, magic missile, undead traits; Resist fire 10
OFFENSE
Speed 20ft.
Melee mwk glaive +8 (1d10+5) reach
OR armour spikes +6 (1d6+5)
Special Abilities Bulwark: all adjacent allies gain soft cover
STATISTICS
Str 21, Dex 15, Con ---, Int 8, Wis 10, Cha 12
Base Atk +1; CMB +6; CMD 10
Feats Dodge, Combat Reflexes, Improved Initiative, Toughness
SQ Armiger Talent (Spear Brace)
EQUIPMENT
Gear: mwk glaive, spiked chainmail, heavy steel shield
As you can see, Gladiator gives a joyous amount of feats over the course of its first few levels, while armiger makes for a wonderful support unit in melee combat. The Grave Knight's Will save was terrible, but they didn't have any primary casters, so it proved to be meaningless.
Juju zombie is a wonderful template though. Definitely worth that mere +1 CR boost.