You do realize there are other modes within TES gaemplay besides conflict, don't you? Reserve proselytizing for those minor tasks, like persuading someone to sell you or give you something, if you will.
Major conflict should always require open/stealth combat, i. e., risking your life to succeed.
Is it not still risking your life if you try to persuade the boss? Your chances of success are minimal, and it's basically a crapshoot, but if you have a diplomatic character that's not as good at combat, then it's worth a shot.
Let me give you an example to demonstrate that more choices do not remove the risk. In Fallout 2, you have to fight a final boss. He's a pretty tough cookie, and a less combat-oriented character would have trouble with him. You can use your stellar computer skills to hack the boss's own turrets to attack him. This reduces the threat, but doesn't remove it. You could also use your conversational skills to convince a team of power armoured soldiers to help you out for the sake of all your lives. Again, this doesn't remove the risk of fighting the boss-- one critical can still kill you-- but it does make things easier for a character that's not all-out combat oriented.
The problem with leaving speechcraft as only helpful for minor stuff, is that it makes the skill useless, superfluous, and a target for cutting. Then we lose another noncombat skill, shift again towards combat and keep doing so until all you have is combat. What's so bad about having quests that can be solved in many ways? It adds replay value (especially if the end result differs depending on the solution taken), and keeps all skills useful and prevents them from becoming superfluous.
Now, I don't expect Skyrim to have some crazy influence system like Arcanum, where every character had an impression of you which affected their willingness to bend to your will, but at least we could have something like the Fallout 2 example. Diplomacy not as an alternative to combat (diplomacy with Alduin's minions? lol), but as a way to alter the way the game plays out.