I found it easier because shielding that fight is too MP consuming. As a SCH, you're either gonna use ET to transform Succor into a big AoE healing (since Lustrate is highly needed in that fight) or burn MP too fast to shield all the incoming damage. As Diurnal AST you have another Regen (which SCH only has if he uses Eos, sacrificing his DPS support) and two AoE skills, one that is very similar to Medica II. That made things easier. However, I'm pretty sure that SCH/AST is a very tough combo and requires a lot of work from both healers.
