If surprise and initiative haven't happened, it's not a combat encounter. Pg266 PHB. Rolling diplomacy doesn't make it one.
Very good. Now notice I did not use the term 'combat encounter' but the word 'encounter.'
There's a difference there. One is the subset of the other. The surprise and initiative transform an encounter to a combat encounter. But they are not required for something to be an encounter.
If there aren't consequences to the action, diplomacy won't be rolled. Rolling a skill doesn't suddenly make something an encounter. The rule of thumb of 1 encounter per hour would be completely blown out of the water. I could quite easily see getting 2 levels a night if you decide to turn every skill check into a skill challenge.
No, rolling a skill doesn't make something an encounter. Being presented with a definate and non-trivial obstacle that the characters must find a way to overcome to progress, makes it an encounter. That encounter might be solved through skillcraft or combat, or just roleplay; that does not make it any less of an encounter.
Invisibility isn't as good as you think it is. It only offers total concealment and makes you unseen. It isn't the same as undetectable. So unless you made a Stealth check, your position is easily discerned simply by dint of you not bothering to hide your presence. (PHB2 stealth rules)
And a single Stealth roll does not override an encounter either. So you make a stealth roll, and are not seen. Gratz. Now you have four other party members that need to be hidden.
Now, that's five rolls, with a single failure meaning the combat encounter is not avoided. Hmmm. Seems like a variant of the skill challenge to me!
Your examples fail. Can you please clear this point up with something a lot more realistic and applicable?
Are you seriously comparing combat which has thousands of pages of powers for, requires a map, takes miniatures and various aids like cards and markers to skill challenges? Good grief.
No. I'm comparing the fact that combat is a more complicated mechanic than a single dice roll but could be resolved with a single dice roll, implying that doing a single dice roll to replace combat is not a good idea. Thus, by analogy, a single die roll is not necessarily superior to a more complex system for the purposes of drama and roleplay. And therefore, a skill challenge might be superior to a single die.
I thought that was obvious, and didn't need to be explained. I apologize if the intent of that was unclear.
Diplomacy said:
Diplomacy is usually used in a skill challenge that requires a number of successes, but the DM might call for a Diplomacy check in other situations.
I love it when reading the skill itself gives you insights into how the skill is properly used.