actually this would be a very good ring for BST situationally. One that comes to mind is when doing Up in Arms 3 BST style. Use this for max mp and then switch it out after the 30 mp is used. You wouldn't have to give up any HP to get a good amount of MP like serket or ether, etc.
And even though it does have -2 STR/DEX, I can still see this being a good ring for DRG as well for the same reason really. Use the mp and change it out. The extra heals could save you.
This ring is a classic example of an item SE created by rolling a random item generator. Seriously could this ring be any more useless for the melee classes that can wear it? Why not give this to the mages?
It 'would' be great for WHM or RDM, if they could wear it. This is good for BRDs or COR/WHMs looking for an mp build. Its not too useful for PUP, BST or DRG with the -2 to STR and DEX.