Mind > Crit = Det > SS
Wildcard: Piety.

My reasoning beyond mind is that crit & det are the only modifiers to our heals. Stacking det is fine, but since AST has no Fey Illumination or Divine Seal, AST is going to really want to maximize what they can get per GCD. At least that's my reasoning anyways.

In addition, if an AST ever goes in Nocturnal Stance, Crit Shields are always better than non-crit shields loaded with DET.