Two strange, uncoordinated SCHs healing together can be sloppy when it comes to AoE heals, but who really cares? Two SCHs can slop all they want and not run out of MP unless they're extraordinarily bad or needing to spam rezzes. It's not as elegant a solution as a single Medica II cast to heal the entire party between unavoidable AoEs, but it will work.

Two SCHs also means two fairies, so despite double Succor being somewhat wasteful, it's not as bad as it sounds. The SCHs just have to either be quick enough to force Embraces where needed the most during major AoEs or at least stop spamming Embrace on the tank so that the fairies can independently heal up the DPS who took the biggest hits. Ideally you have Succor up nearly 100% of the time to help mitigate the impending AoE, anyway, so it's never as bad as it might sound. If the SCHs actually know each other and are coordinated, the potential for damage control is very high.