Conversations with @
Balesir certainly give me the impression that 4e encourages this. Certain 4e mechanics and rules also give me this impression (Skill Challenges, for instance, allowing players to dictate how their skills work, and the poster-boy
Come and Get It allowing the fighter to dictate how eager the orcs are to attack her). I imagine it's possible to avoid that, but that also seems...challenging.
I'm not familiar with your conversations with Balesir, so I can't really comment on that.
I'm not sure what you mean by players dictating how their skills work. 4e has a seriously compressed list of skills, no doubt about it, which by nature makes each one of the much more generalized, leaving a lot more room for interpretation on how they function. Being knowledgable in History now means
all of history, rather than specific parts. I think it's fair for players to be able to add specifics of where their historical knowledge may lie as an aspect of roleplaying, even though they could make a history check on anything under the sun it applies to. I mean it's pretty obvious that Jump only covers jumping and Swim only covers swimming. But Athletics is a pretty wide road, covering Swimming, Jumping, Running, Sprinting, and any number of other things. So while I'm all for telling players what they need to do, I'm certainly fine with players coming up with creative ways to use their skills to accomplish that.
As for "Come and Get It", I understand the intent with the power, it's a taunt, a common game mechanic utilized by tank-types in a variety of video games in order to create "aggro" as a form of crowd control in order to draw foes from your squishier allies to your more defensive ones. Non-magical "pull" effects are awkward formatting, it would be better to encourage attacking the user of such a power with debuffs to attacks or damage upon others rather than forced movement. Of course that was covered under the Fighter Challenge effect and other defender classes similar effects.
AI in D&D, as in other games, is a difficult beast. On the one hand, you can have "smart" AI, which targets squishies and healers first, and while this represents the most likely course of action an enemy would take, it is notably un-fun. You can have "aggro" mechanics, based on some variable numbers such as damage or something, but without a way to control the enemy short of "stop attacking"(which is rarely a good option) is can be difficult to manage. You can have in D&D, "DM AI" which is a weird hybird of smart and stupid AI, sometimes the same foe will attack a viable target, sometimes they'll continue to wail on the tank they can't actually hit.
I support "taunt" mechanics in some form as an effective form of crowd control, especially since it fits into martial themes, but provides them with actions other than "hit them with stick." Pulls are still somewhat awkward for martial classes though.
Though, to the subject, I wouldn't call that determining the world. It's a very micro-level of determination. "Come and Get It" isn't changing how eager all orcs are to attack the fighter, only the specific ones on the battlefield. But then I guess it depends on if you want a type of gameplay where players are always asking
if they can do something, rather than telling the DM what they want to do, and then the DM determining how possible that course of action is.
I prefer a style of gameplay where players tell me what they'd like to do, and I determine how they might go about that.