I generally prefer:
1) State intent (“I’d like to convince the landowner that the goblin threat is real and he should let us march through his lands”)
2) Roll to determine outcome (Failure)
3) DM / player jointly role-play description of outcome and dialogue (Player: “You have a wonderful heard of cattle, Lord Abernathy” DM: “I hate kiss ups. My cattle are the same cattle as my neighbors. Why are you here? Etc.”
I generally prefer:
1) Engage in dialogue.
2) If a debatable point arises, roll to determine outcome.
3) NPC becomes resolved to a position based on the outcome.
This has several advantages. First, it makes dialogue the natural means of interaction and not something that only occurs as a result of a fortune roll. After all, we never really know what sort of debatable propositions might arise spontaneously in a conversation. A player could naturalistically attempt to bluff, persuade, or bully an NPC without a lot of premeditation. This can be fun itself, like player realizing what he's just said comes off as a threat. Ooops. Secondly, humans are linear creatures. We don't like to know the outcome, and once we do know the outcome we often lose interest in the process. This is why most sporting events are live, and watching reruns of sporting events is a fairly rare activity. By placing the fortune as late as possible in the process, we increase interest in the process and make it as engrossing as possible. Thirdly, it means that role-playing dialogue is obligatory (a feature in this case). Under your construction, you can do away with step #3 altogether, and the DM can simply affirm or deny the proposition. Under my construction, it's necessary to at least attempt the dialogue. This ultimately results in more skillful and enjoyable play.
It’s not my favorite but I don’t hate a more player ability influenced game like you are describing, but I do want it to be spelled out clearly upfront that that is the way things work. And I don’t want any options for character resources to be spent on the mental/social etc. abilities that get overridden by player skill.
I don't entirely want that either, but I do want to cultivate player skill. I have a player who is very awkward and introverted and lacks self-confidence. As it happens his character has become the party leader (through a series of circumstances), and his character is also supposed to be fairly charismatic and diplomatic. He stammers and stutters his way through scenes, and is sometimes embarrassed. But that doesn't stop his character from succeeding socially because well, +9 diplomacy check. As a DM I really only care about the content of his words. The dice determine the polish, magnetism, and nuance of the presentation. Sometimes the player in a fit of self-doubt apologizes to me after the session for role-playing so badly, and I tell him that the character is automatically better at these things than he is, or probably anyone at the table is. In the novelization of the game, his words get transformed into graceful and forceful phrases. The important thing is that he convey the content of the message and that he's getting better and better at this all the time, so that there are more and more moments where the character's dialogue is itself a shining moment of awesomeness.
The player gets a bonus or penalty if his content is especially appropriate or inappropriate, but these modifiers are generally small (normally -3 to +3) and knowledge of what content is appropriate is something that the players are expected to learn - for example, another NPC might tell them that this NPC is partial to fish and will look favorably on fish as a present, or they may learn that the NPC cares more about his daughter than anything in the world and may make the appeal on the basis of his concern for her, or that the NPC once committed a great crime and if the players deduce that offering him explicitly a chance to make restitution will make their case more strongly I will reward that with a bonus. Other bonuses can apply based on the NPCs biases. Most of the time the respected cleric of the sun deity is a better choice of negotiator than the hobgoblin outcast, but if you are negotiating with a goblin the playing field is more level. It's actually in my opinion unfair not to apply modifiers in these circumstances because the player - even if he's barely able to articulate - is behaving skillfully. Again, it's not possible to totally remove player skill from the equation - ultimately it the character is brought to life by an intelligence - and really, I don't see why you'd want to.
To me, this is more fun.
I was 12 when I was taught this, and I have been profoundly grateful on many levels ever since. I had been DMing since about 10 for other school kids, and we would say things like, "I introduce myself to the guard." and "The guard asks you what your business is in the town." We 'borrowed' an older DM for a game, and I role-played in my usual manner, "I introduce myself to the king." (or whatever NPC it was), and the DM said, "Yeah, but what do you
say." I was immediately embarrassed, because suddenly my normal fear of social situations kicked in. But, also I was immediately thrilled, because I sensed a whole new level of possibilities. It is the level were an RPG begins to become an art form.