Agreed. When I wrote that it "feels too safe" to me, I was referring to 4E specifically IMO in the sense that there are definite limits on danger and challenge levels. I don't think that pre-4E felt too safe. Some early modules are notoriously deadly, after all.If the game is any kind of sandbox (which it can and should be even if the DM is trying to tell a specific story, as the players can always ignore her and go somewhere else) then there's gonna be stuff out ther you can handle and there's gonna be stuff out there you can't.
I still think it could be done better, I mean built into game design itself, which is beyond the province of the DM.And that's what the DM-as-storyteller is for*. Legends. Local chatter. Setting history. Etc. Couple that with the game at the PH level clearly warning players that there will be times when running is the best (or only) option; and they can't say they haven't been warned.
In real-life, it's usually easy to size up opponents physically (bigger, taller, muscular) and by equipment (unarmed, knife, special ops). You can't do that in D&D often.
In D&D, to get a proper 'spidey-sense', the world itself should have similar coherence. And it doesn't. You can 3 humanoid human-sized monsters, and one has 1 HD level, and one has 5 HD and one has 10 HD with no obvious cues. You can have monstrous giants that are 10 HD and medium sized creatures that are 15 HD. It's OK to have the rare opponent who turns out to be surprisingly more dangerous that it looks, but D&D has almost no correlation between HD and fiction. This makes it rather more difficult for the DM to use the story to signal the level of challenge.