Using or not is just a super simple risk/reward game, I don't like to save scum so when I am in a bad spot and one of the powers is a life saver I use it. Who wouldn't? If we are comprehending games from a realistic standpoint, like a lot of folks tend to be doing here, then fear of death should be motivating enough, shouldn't it?
True...and more potentially....
The reasons why a a particular character would choose to use the powers is because they believe (albeit potentially incorrectly) that the risk reward ratio is acceptable. It certainly seems in keeping with Astarion's character that he would embrace the powers as the tadpole seems to have freed him in many ways. I don't think its immersion breaking for Astarion to believe there might be a way to control the tadpole or at least live with it to his benefit. He's already undead after all.
What if the Absolute is someone like Zariel who is using Netherese magic to create a new being, the "True Soul" a kind of hybrid Warlock. Empowered by the modified tadpole, safe from becoming a mindflayer so long as you remain faithful. There would certainly be some willing to make such a commitment (even if it is ultimately a lie).
