Wasn't Drain and the solo content regen buff both introduced in Stormblood?
I wouldn't have been adverse to it becoming more useful or impactful, but we'd then enter the territory of BLM's being far too universally overpowered. We already do a significant amount more dps than other classes, we already have the best shield in the game, we already have the best situational mobility skill (aetherial manipulation on a 10 second cd) and we already have one of the best downtime management mechanics (umbral soul).As it was, it was a rubbish skill that either needed changing, or removing.
To now want a sustain in the form of heals is a little greedy if you ask me.