Everything in "SET 1" to "SET 5" is rare/ex in the dats, but they all have +1 versions, so it's probably synergy stuff with at least one rare/ex material.
"SET 1" HEAD
DEF:40 Accuracy+12 Attack+12 HP+20 MP+20 STR+6 DEX+6 VIT+6
LV99 WAR PLD DRK BST DRG
"SET 1" HEAD +1
DEF:41 Accuracy+15 Attack+15 HP+30 MP+30 STR+9 DEX+9 VIT+9
LV99 WAR PLD DRK BST DRG
"SET 2" HEAD
DEF:35 Attack+9 Accuracy+9 STR+6 AGI+6 Subtle Blow+7
LV99 MNK SAM NIN PUP
"SET 2" HEAD +1
DEF:36 Attack+12 Accuracy+12 STR+9 AGI+9 Subtle Blow+10
LV99 MNK SAM NIN PUP
"SET 3" HEAD
DEF:34 STR+9 DEX+9 Accuracy+10 Waltz Potency+5%
LV99 MNK THF RNG NIN BLU COR DNC
"SET 3" HEAD +1
DEF:35 STR+12 DEX+12 Accuracy+13 Waltz Potency+8%
LV99 MNK THF RNG NIN BLU COR DNC
"SET 4" HEAD
DEF:34 MP+50 INT+5 MND+7 Magic Accuracy+7
LV99 BLM RDM SMN BLU SCH
"SET 4" HEAD +1
DEF:36 MP+60 INT+8 MND+10 Magic Accuracy+10
LV99 BLM RDM SMN BLU SCH
"SET 5" HEAD
DEF:29 MND+7 Healing Magic+7 Cure Potency+8% Enmity-2
LV99 WHM RDM BRD SCH
"SET 5" HEAD +1
DEF:30 MND+10 Healing Magic+10 Cure Potency+11% Enmity-5
LV99 WHM RDM BRD SCH
DUMB HEAD A
DEF:42 STR+7 VIT+7 AGI-3 Fire Resist+10 Ice Resist+10 Attack+6
LV97 WAR PLD DRK BST SAM NIN
DUMB HEAD A +1
DEF:42 STR+8 VIT+8 AGI-4 Fire Resist+15 Ice Resist+15 Attack+7
LV97 WAR PLD DRK BST SAM NIN
DUMB HEAD B
DEF:30 AGI+5 Attack+8 Enhances "Resist Slow" effect
LV97 MNK RDM THF BST RNG NIN DRG COR PUP DNC
DUMB HEAD B +1
DEF:30 AGI+6 Attack+9 Enhances "Resist Slow" effect
LV97 MNK RDM THF BST RNG NIN DRG COR PUP DNC
DUMB HEAD C
DEF:27 MP+30 INT+6 MND+6 CHR+6 Magic Accuracy+3
LV97 WHM BLM RDM BRD SMN BLU PUP SCH
DUMB HEAD C +1
DEF:27 MP+35 INT+7 MND+7 CHR+7 Magic Accuracy+4
LV97 WHM BLM RDM BRD SMN BLU PUP SCH
MORE HEAD
DEF:40 Attack+30 Store TP+5 Enmity+4
LV99 WAR PLD DRK BST SAM NIN DRG
EVEN MORE HEAD
DEF:43 HP+35 STR+5 Attack+7 Magic Defense Bonus+5
LV99 WAR PLD DRK BST DRG
YET MORE HEAD
MP+30 STR+4 INT+4 MND+4 "Magic Attack Bonus"+6 Magic Accuracy+6
LV99 MNK WHM RDM THF BST BRD RNG SAM NIN BLU COR DNC
No stats yet (5 sets, varying jobs):
新呪われた頭1-5
新祟られた頭1-5
LEGION HEAD (20)
DEF:30 HP+30 STR+8 INT+8 MND+8 Magic Accuracy+5 Set: Magic Accuracy+5
LV96 WHM BLM RDM BRD SMN BLU SCH
LEGION HEAD (73)
DEF:30 INT+5 MND+5 CHR+5 "Magic Attack Bonus"+6 Magic Accuracy+10 Magic Critical Hit Rate +10%
LV99 WHM BLM RDM BRD SMN BLU PUP SCH