Time: After Patch 3.01
Frequency: Always
World name: Phoenix
Character name: Yukino Nadeshiko
Monster name: The Manipulator
Class/Level: Black Mage lvl60
Party or solo: Full Party
In-game time: -
Area and coordinates: Burden of the Father
Steps:
1. Put up both Manawall and Manaward
2. Run into an orb to soak damage (Phase 1)
3. Damage does not get mitigated by either Manawall and Manaward

So...Explosion is neither physical nor magical damage apparently. It still gets mitigated by other spells like Stoneskin though.