In Stormblood, the fairy ends up spending more time trying to keep herself alive than actually healing your allies, which is made even worse by the loss of Sustain since we can't use that to help the fairy get back to high enough HP faster so she'll start using those Embraces on allies instead of herself.
Also, for every time a sch casts Adlo to heal 300 potency (600 if you include the shield/use emergency tactics), a white mage can Cure II for 700 potency and at a vastly lower MP cost. On top of that, we've actually got a 48 second cd on tetragrammaton with 3 lilies, which isn't hard to get, while also keeping a 150 potency per tick regen going on the target, which over 45 seconds is going to heal 2250 potency, so if we're talking about healing over the course of 45 seconds, Regen alone heals more than 3 lustrates, not to mention white mage can also put a 15% of target's max HP shield on the target every 24-29 seconds, depending on lilies. Assuming the fairy actually does keep it's healing going on the target and doesn't end up wasting most her time healing herself, that's approximately 83 potency per second, though less effective than that due to the fairy having lower stats comparatively, so I'll guess that's where you got the 55 approximation. That's SCH's best chance to keep up with white mage, but has become highly unreliable unless you use macros to force your pet to Embrace the target instead of herself, in which case you're going to be ending up with a dead fairy much more frequently and having to spend that 2k+ mp plus swiftcast cooldown to resummon her. It'll vary some on the fight, of course.
You're also going to have more mana problems on SCH if you're using Adlo as much as you're talking about, since the efficiency on it has become horrifically bad.