Right, so Dieter has been charmed or something. The real question is by whom? Pavarotti? Maybe. He's quite the hedonist, but he also showed zero interest in the taxes. It seems to only partially fit at this point, we need more information.
When we officially uncover his hypnotism with Max, I can run with him to the physicians guild and get a doctor that can cure the problems. I can invite Dieter back to the Templar's Arms for drinks that night, and we can have the doctor meet us then. We need to figure out who did this to him, as whomever hypnotizes someone to support taxes, has to be directly linked to the conspiracy at hand.