TOP SGE PoV Rank 1 + Markers P5 - The Omega Protocol (Ultimate) 

I'm using the standard 2.42 min piety set on the balance with a pentamelded crafted ring

Heya! Pepsis indeed isn't a common button for usage, but it can be useful in some areas of gampelay! First off and most importantly, it's generally a panicky button that you can use in case your regen healer is dead and you're looking for quick healing output. Doing Eukrasian Prognosis > Pepsis > Eukrasian Prognosis is the fastest and most efficient way to heal and shield up the party if Pneuma and Ixochole aren't available to you. You can use Pepsis to heal as well during downtime mechanics using the same combo. Eprog > Pepsis > Eprog is a very simple way to give everyone a nice boost. Next to that, there are SUPER niche usages. In Zeromus, the fight starts with a 1 hp mechanic where you need to heal the party to full hp. You can shield pre-pull, then use pepsis to convert that shield into healing once the mechanic hits. One more nice usage of Pepsis, is that if you shielded too early for a mechanic, and the shield will run out before the mechanic hits you, you can quickly delete and reapply everyone's shields to refresh the duration to 30 seconds. Knowing when to use this is once again a niche skill, but it's an interesting piece of tech! The final usage of Pepsis I can think of right now is in a currently badly documented LB-cheese, but you will never use this in your lifetime if you're not a hardcore speedkiller. So TLDR: Pepsis is indeed an uncommon usage, but is most importantly used in moments where the Regen healer is missing or dead to help heal up the party using Eprog > Pepsis > Eprog.

@@CaroKannffxiv tysm for answering, hopefully I can improve soon ^^

Good luck! Feel free to ask me anything