But you bring up an interesting issue that the game ramps UP it's contexual difficulty as you play.
Let's break this back down into the two categories I've mentioned before. AI, and Stats.
In the games with a downward difficulty scaling, as you mention. Often times what is happening is that the AI is increasing, but the player's raw stats are sky-rocking to the point where even if the AI is more complex, they can just bully their way through it.
In DS, the AI improves, but the stats also skyrocket to surpass even the player's stat scaling. What this does is force the player to step up their game (The equivilant of the Game's AI). Sadly, this often just leads to the player finding the nearest, easiest exploit.
So, given the context to this, would you reccomend that SE adopt the policy of having their stat scaling curve upwards sharply for their monsters? I can see some of the attraction in this, particularly in something niche like epic world bosses, but ultimately I feel as if this sort of scaling should be best reserved outside of the main storyline.