Round 2!! Field Armorer (warrior group AC buff) is blocking/overwriting Armor of the Inquisitor AA due to Slot 6 "Increase AC by". Sooo lets do some research!
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Slot 1
Heartwood Skin (Druid targeted/group "Skin" buff)
Slot 2
Armor of Unwaivering Faith (Paladin self-only "shielding" buff)
Slot 3
Cloak of Feathers (Ranger targeted AC line)
Slot 4
Gallantry (Cleric/Pally targeted/group Aego buff)
Order of the Devout (Cleric targeted/group AC buff)
Slot 5
Bracing Defense (war self-only AC buff)
Preservation of Tunare (Paladin self-only defensive proc buff)
Slot 6
Armor of the Inquisitor (Paladin self-only defensive AA)
Field Armorer (war group AC buff)
Slot 7
Fortify Companion (Pet-only Buff)
Charge for Power (SK self-only hate over time recourse)
Theft of Pain/etc (SK self-only AC Tap line)
Torrent of Pain (SK group AC Tap....but its only 12 AC lolz)
Slot 8
Empyrean Warder/etc (Mage self-only buff line)
Celestial Tranquility (monk self-only haste clicky)
Slot 9
Spirit of the Wood (Druid group AA buff)
Convergence of Spirits (Druid targeted AA buff)
Slot 10
Form of Defense clicky
Prismatic Ward clicky
Slot 11
Third Spire of Divinity (Cleric group AA buff)
Third Spire of Holiness (Paladin self-only AA buff)
Slot 12
Champion's Aura Effect (war group AC Aura)
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Pretty easy here. Armor of the Inqusitor can go on Slot 7 or Slot 8....those are all Self-Only or Pet-Only, and should not conflict with anything else (again please verify on your end). Slot 8 looks the least messy.
And....while yer at it....if you want to free up a Slot for future abilities, you can take all those Self/Pet-Only AC buffs on Slot 7 and put them all on Slot 8 (or Vice Versa).