I agree that the current skill checks are not done well. What actually annoys me most is waiting for that damned die to roll - and if you click space to make that wait time go away you never know if you failed or not. Infuriating.
But, especially with Nettie, there's another view of the situation. Even if you fail the dialogue checks, that is not a total failure of the situation. You still have 3 or more ways to solve it, and the in the end the game continues the same no matter which you choose - the only thing that changes is how much loot or xp you gain from it. And the peaceful solution, through dialogue, is as always the worst outcome here.
- You can cook your own cure in the cauldron outside
- You can pickpocked the cure.
- You can simply kill her, nobody cares. Then loot her room. Nobody knows, nobody cares.
- Just die and ressurect - didn't actually try this, guess it might work ?
So in then, it's all the same.
I am not sure if there are any dialogue checks which have a really hige difference in the outcome. The one I can think of is the outcome after the 'evil ending party'.
If you convince the drow priestess to help you, she sends to the overland route - if you fail and kill her I think you might have to go through the underdark ?