I was just thinking of a similar build, and was just thinking of switching Chest to Infusion, and adding some All Resist to increase Damage Reduction for the Shield, add Masochist, Harmony, one Regeneration, and Equivalence. any heal for the HP also helps keep MP up, which is good for the Mana Shield. and the Masochist Set increases damage while HP down. just need to make sure enough HP so heal doesn't kill you while your Shield is up. with so many new builds doing huge damage to get through the thick HP/Damage Reduction builds in the Arena now, you are going to need a decent amount of Damage Reduction for the Mana Shield, or you wont have a chance against someone who has a lot of DR for their HP. or skip the Equivalence, as that might not help enough and actually hurt more than help. just thinking and typing out loud.
@FairyTail & @dickwad I have come up against some good Mana Shield builds in the Arena, but I don't know how far any of them have gotten in the Arena. I have met a few of the good ones in Eternal League, but depending on how good their crafting is determines who wins, as I am still using my Farm Build. I think a Mana Shield PVP Build is viable, but you would have to think way outside the box. maybe move into another box and try to think outside that one.