No, the other plate pieces, vambraces, bracer, boots etc all have more AC than their Fallen Saint equivalents. This is the only anomaly among them all. The cleric helm also has less AC than Fallen Saint, and I would bet the warrior and sk helm once added to the database will also have 70AC, which is far less than the Fallen Saint.
Atathus`s Warfire Vambraces
MAGIC ITEM LORE ITEM NO TRADE
Slot: ARMS
AC: 88
STR: +30 DEX: +25 STA: +35 CHA: +30 AGI: +20 HP: +465 ENDUR: +435
SV FIRE: +25 SV COLD: +35 SV MAGIC: +30 SV POISON: +35
Stun Resist: +5% DoT Shielding: +4% Attack: +35
Required level of 75.
Effect: Ferocity VII (Worn) at Level 75
WT: 6.0 Size: MEDIUM
Class: WAR
Race: ALL
Slot 1, Type 8
Vambraces of the Fallen Saint
MAGIC ITEM LORE ITEM NO TRADE
Slot: ARMS
AC: 81
DEX: +25 STA: +40 CHA: +30 WIS: +30 INT: +30 HP: +335 MANA: +335 ENDUR: +335
SV FIRE: +25 SV DISEASE: +25 SV COLD: +25 SV MAGIC: +15 SV POISON: +25
Shielding: +3% Avoidance: +10 Strikethrough: +7% Attack: +30 Regeneration: +4 Mana Regeneration: +4
Required level of 70.
WT: 6.0 Size: MEDIUM
Class: WAR CLR PAL SHD BRD
Race: ALL
Slot 1, Type 8