I perceive a world where it's impossible for the PCs to run across encounters significantly outside their CR (high OR low) as video-game DMing, just as much as having predefined encounters is video game DMing (I'd also love to meet a DM who is so adept at adapting on the fly to PC actions that they don't notice the adapting when it's done, but I digress). I perceive a world where player choice leads to TPKs as being bad DMing, and have been called a Bad DM in these parts for having that particular circumstance arise.
Please note that the example of the guards, the king, and the throne room was veekie's, not mine. I have not posited a specific example, and would be genuinely interested in examples of story arcs with encounters that aren't predefined such that it's impossible to "skip to the end."
Sure, and when they do run into those encounters, it should be through the choices they made. Specific choices, that is, not "we turned right at the fork and there was a CR+8 encounter down that hallway". And you wouldn't have to look very far; I can't speak for my own players, but my DM operates very much the same way I do, and I would be hard pressed to figure out what was pre-planned and what was changed. It's alot easier, of course, when you come up with an overall narrative arc to begin with, and build the story as an organic whole. Then you can see the consequences when the players start to make choices. I highly recommend picking up one of the FATE system books if you want a good methodology of how to build encounter maps that can be adjusted on the fly.
As for your second point, that's easiest to do when the plotline is all about, or at least partially about, figuring out who the BBEG is - divination blocking isn't that hard to get, and for a genuine baddie, should really be a way of life. One method is to leave it as a question even in your own mind, (though have the stats drawn up ahead of time) and then the follow where the players go in their search. And when they "figure it out" - they feel clever, and you look like a genius, and everyone goes home happy.
I
regularly see posts and hear comments (almost universally negative) from folks about being able to tell when a DM is adjusting stuff on the fly, even in a PbP medium, so I'll chalk that up to different experiences for the two of us.
Divination blocking feels extremely passive-aggressive to me; it's basically the DM negating player choices without telling them beforehand that he'd prefer a game without Scry-and-Die tactics, which is what Divination blocking creates. It may be a solution to a particular problem, but it opens up an entirely new set of problems in the game's dynamic. That said, I've run - and seen run - several games where the plotline is about figuring out who the BBEG is; it has yet to preclude the PCs circumventing key elements and discovering the answer by dumb luck, and thus dealing with the BBEG when they're not as prepared as they probably should be.
That's not the kind of thing that I can answer in detail without specific examples -- every situation will be different. But it's absolutely plausible that they would come upon the BBEG while said BBEG is still getting prepared... and so, for example, they make Listen & Spot checks to observe the BBEG discussing something with a minion that reveals some aspect of the BBEG's abilities that they're not prepared to handle, or they make a Knowledge check and identify the BBEG as something way over their heads, etc.
If they are making Listen & Spot checks to hear what the BBEG is discussing
that leads them to realize they're in over their heads, what they're also hearing is a
vox dei hint that they're in over their heads. The difference is negligible, and depends entirely upon player buy-in, from my experience. I've said before that I've been at more than one table where hearing/seeing such things in character led to OOC quips from players about having gone off the rails. As for the Knowledge checks, those would usually rely on either the player making an assumption that their actions haven't (necessarily) indicated is valid or invalid, or on the DM dropping some variety of hint - heavy-handed or otherwise.
What, so the party bypasses the halls of the three story building to get to the throne room so suddenly the guards outside do, too? I'd have trouble with that level of suspension of disbelief, personally.
Were there no guards on the 1st, 2nd and 3rd story of the building? And no guards right outside (or inside) the throne room? That's some overconfident (or stupid) king right there.
There were guards on all three stories of the building. They all figured into the overall challenge that the castle would present to the party, and into the resources available to the party when they faced the king. The party bypassed a majority of those guards, and thus a majority of those resources. How, precisely, would you propose that all those guards and resources get to the king's throne room (sleeping quarters/where ever the party encounters him) in the 2 - 4 rounds that the boards generally presume typify an appropriate battle length for 3.X D&D? How, precisely, would you propose having the PCs deal with all of them arriving in a stream, or a pile, without the encounter being a TPK or feeling artificially defused?
