Once again, if the fighter exploits were explicitly metagame and affected metagame things only, I wouldn't mind at all.
I understand that exploits are not explicitly metagame. In this way I think of them as like hit points - depending on one's take, they are either flexible or incoherent!
But what I'm missing, I think, is why you think they
can't be treated as metagame. In what way do they
not affect metagame things only? Maybe there are some rogue powers that I should have in mind but am forgetting about (I'm not really up on my 4e rogue knowledge), but for fighters they're basically more attacks, more damage and more knockback/down, and for rangers they're basically more attacks, more damage and more movement.
The damage boosts and knockback/down strike me as bascially dice manipulation - analogous to using an explicitly metagame option to reroll or boost damage dice - and the additional attacks seem to me basically to be manipulations of the action economy, which as I've said seems to be obviously metagame (because of it's stop motion implications if treated otherwise).
It's not a purely metagame thing. Goblins can run 120 feet in 6 seconds. A 6th level barbarian with pounce can make 2 attacks on a charge and can charge 80 feet in 6 seconds. "From where you are standing now, is it possible for you to kill all four goblins before they run out of the [dungeon/canyon/etc.]?" is a question that that barbarian can answer purely with in-game knowledge: Yes, he can run and attack that fast, and if he strikes accurately enough he can down them all, because he knows he can charge that fast and he knows what he can do.
What you describe here might make more sense in a system of continuous action - B/X and 1st ed AD&D were something like that, I played a version of 2nd ed AD&D that was something like that (Combat and Tactics, I think - and even core 2nd ed initiative was continuous action also, wasn't it?).
But in a turn-based system, it's more complex than that, because the barbarian's ability to catch the goblins depends not just on relative speeds but on who goes first in the initiative sequence. And brings into play the minutiae of the charge rules. And we haven't mentioned action points yet.
And that is even before we bring in the vagaries of the dice. So, in the fiction, the barbarian knows that on a good day he can catch and kill those goblins. Mechanically, maybe he can if he has an unexpended power and rolls well with his attacks and damage. And the player playing the PC has many ways to RP this, depending on the resources s/he has to hand, from "Don't worry, they're as good as dead" to "I'm not feeling that lucky, better get your bows and crossbows out if you want to stop them!"
I mean, this exact scenario has come up multiple times in my game (involving the ranger-archer rather than a barbarian). One time he had Biting Volley left, and killed the fleeing bad guy on a crit on a 19. Another time he had only Twin Strike left, but still managed to crit (on a 20) and bring down the fleeing bad guy. The RP and narration didn't have to change. I don't think he's yet brought down a fleeing bad guy using Combined Fire (a single arrow as a reaction to an allies ranged or area attack) but I could easily see it happening - the ranger has already acted, then the bad guy flees, but the wizard attacks with a readied Magic Missile and the ranger follows up with Combined Fire. The narration wouldn't have to change.
You don't have to have magic with names and martial stuff without
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As long as you treat mechanics as having some actual manifestation in-game, it doesn't matter whether you call something magic "the fireball spell" or "a spell to make a large explosion of flame" or whether you call a maneuver "the Whirlwind Attack maneuver" or "that thing you do where you swing your sword around and hit everyone around you." They can be equally arbitrary or equally non-arbitrary. That doesn't happen, however, if you treat one or the other as purely a metagame construct.
I don't think I get this either. Why do encounters and dailies as metagame stop named martial manoeuvres? In the fiction, the fighter PC performs "Whirlwind Attack" - but on some occasions, its mechanical impact is limited to one target. (Or, if that seems too much trouble and/or too inane, the fighter player can use Passing Attack, say, as one manifestation of his/her PC's Whirlwind Attack, although if there are 3 or more adjacent enemies it will only ever hit two of them.)
you've just undermined your own question due to the Attack of Opportunity Rules. What the barbarian needs to to is be able to get in position to threaten them all - if they try to run away then he's going to be attacking their backs anyway. The answer doesn't revolve round whether he has a recharged close burst 1 power, it revolves round positioning. If he has a CB1 power, he might get a second swing at them.
I think I agree with this, at least to the extent that the OA rules are part of the mechanics that break down the rigidiy of the turn sequence, and thereby (i) increase verisimilitude (it's not a stop motion world) and (ii) make more room for a range of non-process-simulation understandings of what is going on with limited use martial powers.
In the fiction, at least as I see it, there is no great difference between these mechanically different alternatives: (i) the goblins going first, the barbarian going second, giving chase and taking down only 1 goblin with a normal charge, or (ii) the barbarian going first, closing to threaten the goblins, the goblins then running away and the barbarian killing one with an OA but missing the others, or (iii) the goblins going first, the barbarian going second, giving chase and then attacking with a close burst charge power but killing only 1 goblin while missing the others.
In contrast, a 4e fighter's AoOs are likely not good as his exploits damage-wise, even with Combat Superiority and Heavy Blade Opportunity. The extra [W]s and riders can make a big difference, so "daily exploit that hits 2 people" and "make an AoO against 2 people" aren't the same thing.
But there are so many moving parts here - for example, what does hit point loss for goblins equate to in the fiction?
Imagine in a Fate Point game, the fighter player knows that if s/he spends a Fate Point on an attack it will probably kill a typical goblin, but if s/he doesn't it probably won't. What story does s/he have his/her PC tell, within the fiction, about his/her goblin-killing capabilities? Maybe "I might one-shot it if I'm lucky!" Well, the 4e fighter player can say the same thing - after all, the bonus damage on a crit from a lucky OA attack roll will probably compensate for the extra dice that an encounter or daily power might have generated.