Yeah, it is disgusting. However, if it were *just* that, I could envision a character swallowing their disgust and going through with it in order to gain psionic power. As it is, though, it also damages your brain and undermines your mental integrity, making you less you every step of the way. And to do that, you must be utterly mad.
I get your position on this but it is not looking at the lore or the characters. A Wizard, bent on gathering as much power as he can would embrace the Tadpole and seek to bend it to his will. As might others. However a Cleric or a Paladin with a "good" bend would resist it at all costs. The Tadpole is part of a plan to create a new (false) God and this would be opposed. BTW this little tibit is revealed EARLY in Act 1 before the pressure to strengthen the worm comes into play.
Further consider that the purpose of the worm is the rape you of your body and mind, forcibly take away your freewill. There is more that disgust at plan for many people.
I do agree with some of the comments here, the worm changes feel like they are last minute. There is no alternative, it feels forced, almost on rails to a specific direction. If they had given you options to cure yourself, or consequences to using the power or not, then I would say it was a solid plot tool. As it stands, when you reach end game, the entire mechanic feels contrived and forced in at the last minute.
