I really like Pepsis in particular because it changes the timing of your shielding to be more intuitive with the way a Scholar plays to avoid overwriting each other. Scholar has bigger shields so they are the logical choice to use a GCD shield for the party before damage comes out if needed. Once a cast bar for a raid wide starts a Scholar who still needs to GCD heal is going to use Emergency Tactics to transform their next Succor or Adlo into raw healing. A Sage in the same party would use Eukrasion Prognosis/Diagnosis to burst heal AFTER damage goes out to take advantage of Pepsis and convert their barriers into more healing. Emergency Tactics tells a Scholar to Shield before damage happens. Pepsis tells a Sage to Shield after because if the shields are absorbed by damage Pepsis can't be used. If you understand both toolkits you shouldn't ever be overwriting GCD shields and this entire situation assumes that both healers are completely out of oGCDs to begin with. I'm actually very pleased by the shield healers synergy. Pepsis is clever in that regard although it feels very odd for anyone coming from Scholar since it's the reverse of what your habits are.