Kovi: Well, the rules I have at my disposal say that the Disciple level of Authority increases the effect of threatening in the dialogues. Wisdom handles spells (their mana and stamina cost, penetration and regeneration), while Perception handles secret objects (the visibility of items scattered on the ground, secret doors, buttons, stashes and traps, it also decreases damage caused by the traps or the effects of Blinding).

Generally speaking, I was told by the dev that the effect of stats or player's actions on the dialogues is lower in the end than it was originally planned. In the rules, there are concepts of the NPC's Awareness (checking if the NPC recognizes the PC due to his Fame (affected by how many - and how difficult - quests the PC has completed)), the PC's Popularity with the NPC (affected by the NPC's Alignment based on his/her Archetype), and the NPC's Tolerance towards the PC (that for each conversation topic defines the level of Popularity required for the NPC to be willing to discuss that topic with the PC). And it is hard to guess how much of this was truly implemented into the game (for example, you can affect your Popularity with some NPCs by completing a quest for them which will allow you to discuss a required topic with them - this is something you have to do with Ellisia Würtenrodt if you have completed a quest for Theil Brechthold before). And you can greatly influence your Popularity with NPCs during your initial conversation with them (this can be seen when talking to the priest Romius, for example).

As far as the lack of min/maxing goes... well, you will see for yourself. I think that you won't receive enough skill points to be able to max all your skills (maxing out abilities was much simpler with my priest), so theoretically if you invest too much into some skills that are "not that useful" you could lack these skill points in some other skills that are "more useful". But as was said, you will see for yourself how it turns out in the end.