I suspect this might be by design and part of why those ''special'' people are infected by tadpoles in the first place. But it can be what you said too, we don't know yet.
I'm not buying that. Those special people with desperate conditions are the ones who
don't need to be mind controlled, because they already have a strong motivation and can be bought.
Astarion - serve us and we will free you from your master.
Karlach - serve us and we will free you from your master.
Gale - serve us and we will remove the time bomb that kills you.
etc...
For True Souls, they are much more a liability than an asset. What if Cazador / Zariel comes looking, or a Netherese orb blows up in Absolute HQ.
