Tadpole weakening the subjects does not make sense. Why would they want their mind controlled true souls weakened? How would powerless slaves ever be worth the effort? Minthara and Ragzlin are not level 1.
I agree with you on this point, which is one reason I'm looking for alternative explanations for the companions' power levels. And while they may not be perfect, I think they exist.
With respect to the overly epic back stories of our companions, I'm not so fussed. Okay it's not realistic, but I'll sacrifice that for the sake of some ripping high fantasy yarns as we get to know them better, especially if those tie in with other elements of Forgotten Realms lore and help me learn more about it.
Besides, it looks as though they're going to have to be able to hold up their heads next to Minsc and Jaheira who were level 30 odd last time I saw them. Okay, not true as I did read the more recent Minsc comics and the third one has a mocked up character sheet for him at level 6, implying statue Minsc might have started out at around level 4 if each adventure constituted a character level. But I have no idea how they can make Jaheira convincingly a full companion at a comparable level to our party. If the answer was that she got nerfed by a tadpole I will be most disappointed! In that case I think I'd prefer her to be a powerful advisor and quest giver than a companion, but I guess I should wait and see what story line Larian have in mind.