While the post borders on trolling, because of how absolutely useless Drain was, I agree that it's sad it was removed as it was good flavour (together with Protect).
IMO a better solution would've been giving Drain a higher potency, a long Cooldown and making it into the spell to use after Conversion saps 20% of your max HP. Sadly BLM instead lost both Conversion and Drain, in favour of Manafont, which is just a flat and boring "restore mp".
It would have fit in there very well too since after Conversion/Manafont you only have enough MP for two more Fire 4 and the space to cast a 3rd spell before going into umbral ice.