The amount of damage and healing from Drain is completely overshadowed by the Light Side healing abilities. People in the Discord are actively telling newbies not to pick Drain because it’s just that much of a setback. The only characters who have it, have it for flavor.
I think Drain should have better scaling than Force Heal for both healing and damage. Yes, that makes it the better mechanical choice, but there are other factors to consider.
Force Heal can be justified for Light, Gray, and Dark Force users, while Drain is pure evil. Taking Drain locks you out of Benevolence, which ALSO scales with WIL. Therefore, the extra damage and healing can be seen as a balance for giving up a second, even stronger healing ability.
I would also reiterate my suggestion from last year that Drain be earned through RP, since the lore says the only way to learn it is to have it used on you by someone else.