The thing is that as you gain levels, your health goes up more and more. Potions only heal a fixed amount, no matter what level or stats you have. For that reason alone, they get less and less effective the more you level up. Cure Wounds is not the best healing spell certainly, but it does scale with your level (and STR). Scaling is what makes magical healing good.
So no, it won't be super if you're just slapping it on a rogue with 5 STR, but put it on a warrior with 14 STR and it'll be a lot better.
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On my current run I have put Glass Cannon on crossbow-using Bairdotr. She's a murder machine, especially with Oath of Desecration slapped onto her.
