If I may, I think the issue you are having here is presuming a single answer for all situations. That's a 3e approach. A power does X and it always does X and it always works in exactly the same manner is how 3e (and for the most part, earlier editions of D&D) operated.
I wouldn't really call it a 3e approach, as I learned that paradigm from BECMI, AD&D, and virtually every other RPG that I played as a teenager. Sure, there were exceptions (although I can't think of any off the top of my head, other than explaining what hit points represented or one attack roll representing 10 seconds or a minute of combat).
The power's effects change depending on what the PC is facing. A humanoid becomes enraged, flailing wildly, thus dies easier as he forsakes his defenses. A skeleton obviously isn't going to be enraged, but, perhaps the bard's running commentary reduces the horror that the rest of the group feels when faced by undead abominations reaching from beyond the grave, thus making everyone else a bit more effective - again simply mechanically realized by lessening the skeleton's hp.
That's the entire point of decoupling the mechanics from the narrative. You know what happened - the skeleton took X psychic damage. How did it take that damage? Pick a method that makes the most sense in the context of what you are doing at the time.
I understand the decoupling of mechanics from the narrative and what it entails. I just don't
like it very much. The inexperienced players in my group have a particularly hard time with it. They expect that they will describe to me what their character is doing and then I tell them what happens as a result. Sometimes these actions need to have rules applied to them and the effects described in terms of game mechanics, and sometimes they don't. The powers in 4E generally require players to think in terms of what mechanical effect they wish to put into play and then describe how this was accomplished in terms of the narrative.
That's counter-intuitive to me, and my casual players find it even more so.
Either way, the player does have an end result in mind, but the "traditional" way leans towards determining the game mechanics effect from the narrative context, while the 4E way leans more towards determining the narrative context from the game mechanics effect.
In the first case, I feel like I'm interacting with the imagined world and its inhabitants and using the rules to facilitate that.
In the second case, it feels like I'm interacting with the game mechanics directly. This doesn't make the imagined world or the narrative irrelevant, but it's hard to shake the feeling that the game mechanics are the focus and the narrative is just fluff for my amusement.
This is entirely my own perspective (one which most of my players seem to share), and it is certainly not going to be shared by all players. I think that 4e demands a specific type of creativity from its players in order to really shine. Some players will really enjoy coming up with new descriptions as to how their powers work in different contexts, while others will get tired of it in short order. Using
Viscious Mockery to incite rage in a bandit, orc, dragon, or goblin? No problem. When you've used it on oozes, slimes, skeletons, puddings, stirges, zombies, and now you're faced with an iron golem, you might just feel disinclined to explain a 1d6 + Cha mod psychic damage effect that inflicts a -2 penalty to hit for 6 seconds yet again.