This head piece is great for BLM.
First, if you've got the INT already backed up to get the damage multipler, the Magic Attack Bonus+2 is always a great aid. MP recovered while healing is always a plus. The MND helps your White Magic enfeebling spells and enhances your Stoneskin's power for /WHM or /RDM. I'm pretty sure the -Enmity is self-explainitory for any BLM considering those high tier nukes can be pretty "attractive" for the mobs. For your Black Magic enfeebling spells and elemental debuffs just macro in your Wizard's Petasos or INT+ head piece for them, but this piece is a great asset to any BLM in enhancing his damage output with those helpful benefits on the side.
Side note: The Refresh effect is +1 MP/tick with the full set, but take into account if you have the full set you can continue to regain MP while casting and resting, and not have to macro in your Black cloak everytime you aren't acting.