I like what Saeviomagy says, but I'm going to agree and disagree with him on a few points.
Don't expect mechanically minded people to stop trying to powergame just because you're denying them information. It won't happen. You will get immersion by making the non-mechanical aspects of your game interesting, engaging and polished, not by trying to ban the mechanical aspects.
I have to agree. Gamers will attempt to identify resources, the powers of those in regards to their current game objective, and then min/max their strategies to accomplish the goal. Just because the mechanics are behind the screen doesn't mean the behavior will stop. So making the mechanics better designed is the goal of a good DM or any game designer. I don't think you, Doc, are talking about dropping or banning the mechanics, just sticking them behind the screen. Exploration immersion may be increased by hiding them, but character immersion not necessarily so. And min/maxing to win the game likely won't stop at all as long as the situation is treated as a game.
Finally: Calling anyone who likes the mechanical aspect of a game a power-gaming munchkin is pretty offensive, and it's likely why you're getting negative responses.
I agree again. Calling out power-gaming is like calling Spassky a bad chess player. Attempting to accomplish an objective in a game is often the point of most games. Playing other systems where all these rules are in front of the screen may have soured you from this behavior, but having no ability to either Rules Lawyer (the rules are hidden) or min/max stats or class progression (these are also unknown) leaves far more time for these mechanically-minded players to focus on the role playing situation at hand.
First up, D&D is not the game for this. D&D classes are straightjackets that limit mechanical character development to a narrow channel and punish diversity. It will become very obvious to your players what numbers are what, to the point where you may as well not bother with obfuscation. The only way you're going to keep everything hidden is if you rewrite the character classes, spells etc etc, which is way more work than is necessary when there are great games out there that can do this for you.
Here I have to disagree. D&D was the first wargame/simulation game to become a cooperative design and then have it's rules hidden behind a screen. If you hide the rules, try and treat them like codes. You will need a scope for the players to play within. Think of the game Mastermind. It includes color and spatial positioning. For D&D you will have those two and many, many more, but you will still need a scope within which to code break. The class (social role) is the original way of doing this. You don't have to do social role role-playing, but it was what D&D was originally designed for. And Saeviomagy is right that having an unknown rules set/code is pretty much the point in such a game. Why play Mastermind when you've already peeked behind the screen?
Incidentally, modeling your game off of oblivion is a terrible idea. Just refer to any of the powergaming guides to oblivion for reasons why. Powergaming in oblivion is simple, and it's a matter of doing very repetitive, boring things over and over. Making your roleplaying game reward tedium isn't a good thing.
I don't know Oblivion, but tabletop RPGs don't work like CRPGs. My nephew plays Runescape for hours every week, but our D&D group creates SOPs, standard operating procedures. We simply say "we do this for the next 4 days" and our PCs do it. Grind is only an issue, if the players continue to beat their heads against the wall for every situation instead of developing plans. And it's not like a change in a similar situation isn't noted. As the Ref narrates back the summary of 4 days of say, logging and campfire building, we can stop him or her at any time to make adjustments, or bring game time back in line with real time and address the situation anew.
Learning how to set goals, make plans, develop routines for the PCs, and debate strategies for potential future moves is a big part of D&D from my POV. I think you're on the right track, if you are looking to push players to engage in those behaviors.
Just make sure you get their okay first that this is how they want to be pushed.