Galvanize vs Galvanize, the largest shield wins. Typically I will Adlo the tank then succor the party, since the tank's shield will fall quickly, but the party has up to 30 seconds to benefit from it. Adlo will also deteriorate before stoneskin, so if you can get it back up before stoneskin breaks, you've got even more time. Deployment Tactics + Adlo work well on a Warrior in defiance if you know your party will be taking heavy damage immediately.

When working with a Nocturnal stance Astrologian your shields will be interchangeable. Whoever casts theirs last, no matter how small, overwrites the other.