The current changes to Lavender Refrain have made the perk a bad choice for any build to pick as mana as of now with this mod can be used by any class for some use. With this perk that is no longer the case, and you can't even be a mana tank anymore due to this change. I know the perk was overtuned and needed a nerf but this was a bad change as it removed a whole play style of using mana as a tank.
This perk worked alongside Mystic Incision and it's nerf to enable a duality playstyle with mana, use mana for damage at the risk of losing to much health and losing the trait from Mystic or keep the mana for tanking. It was genius and fit the whole idea of being umbral.
The changes I think it should of had was lower mana item potency to 0% to remove the broken aspect of unlimited mana healing and increase the mana regen delay a little bit as well.