Nah, if Sage isn't given any buff, why would you bring a Sage? Just bring a SCH.
Happy is... Not the youtuber I'd quote, he has a respectable experience with the game but not all of his words are the absolute truth. IMO they're often far from the truth and the kind of guy to be baited by flashing things, but that's another topic.
Sage will inevitably suffers the comparison from SCH.
A lot of tools are much better than SGE's tools, Protraction, Expedient, Excog are all amazing tools.
In comparison SGE got Krasis that traded 10% max hp for 10% healing (on all action, including tank cooldowns).
Holos and Expedient, Expedient wins.
Reason behind that is simple to me, Holos has a heal AND its mitig lats 20 seconds. Where do you use that? During a long series of raid wide? Before those raidwide when your team will be already topped?
Expedient can be used before to snapshot the most raidwide and has the sprint if you need to move. I can think of a lot of situation in ultimate where Expedient would've made a lot of players nerdgasm.
On top of that, SCH has Fey Blessing that is probably the healing part of Holos. SGE is SCH but with a lot of button merged together. You have to press less buttons but you don't have the flexibility, if you want to mitig AoE you will use Kerachole and/or Holos, SCH can use Sacred Soil and Expedient, then use Fey Blessing.
Pepsis is okay but will never be considered for single target healing. The only scenario I can see pepsis used is after a transition when there is no target and your team lost a bunch of hp.
Or your team needs to move a lot, there is no target and you need to heal during that time, UCOB and Heavensfall or example. If there is a target and you need Burst Heal, Zoe+Pneuma.
Even then, on my test with current BiS, 2 Progonis heal for 11k, Eukrasian prognosis + Pepsis heals for 1.7k and 6.4k respectively. I can't think of a situation where your shield is half damaged and you want to break it, that would need too much setup of a low reward when you can just have your AST using its Star or Zoe+Pneuma yourself.
Oh and Ixochole heals for 7.5k.
Then, the weakest tool of the whole SGE kit is in my opinion Rhizomata. Its cooldown is too high for its effect.
It has to be compared to Recitation that makes an ability free and critical. Not only "free" means you can use it at 3 aetherflow, there is also a critical on it!
IMO, SGE wins on SCH with Kerachole and Pneuma, despite its cooldown far too long. I can't be exactly sure about Seraphin and Haima/Panhaima.
Other than that, SGE should remain good enough for harder content.