I don't think "constantly" is the correct word.

Dark Arts for Dark Dance every 60s.
Dark Arts for Dark Mind, is only needed for magical based attacks, so not terribly often.

A simple Delirium Blade -> DA/Souleatter rinse repeat will maintain a 246 average potency which is higher than any other tank, AND maintain your MP so you can use it for CDs. If you really want to throw heat you can just spam DA/Souleatters but you will burn out quickly.