Arguing narrativism doesn't do much here; the point of the rant was not whether a wizard is less a wizard then a multi-classed uber-caster, its the fact that statistically he's under performing.
Take my fighter example; the ftr/PDK/KP has a boatload of options available to him; bolstering allies, bonuses to saves, new offensive and defensive manuevers, better skill choice, etc. What did he surrender for it? seven feats (while nothing to sneeze at, he gained well over seven unique abilities in this build). The trade-off ratio doesn't equal.
The thrust of the multi-classing mechanic is allowing the character to choose breadth vs depth. Usually a MC gains depth and looses breadth although your particular example is the other way around since he'd lose access to the upper level fighter specialization feats in exchange for his abilities. Is it worth it?
That very much depends on who you ask. It probably depends on the exact party composition and campaign type. From a pure damage output stance I suspect he's lagging the straight fighter who has access to the mastery feats. And at some tables that's what would matter.
My point is that there is no one "right" way to play the game in any aspect, including character creation and growth. There may be wrong ways, a hyperactive, caffine overdosed teenager trying to figure out why his bard 1, psion 1, sorcerer 1, wizard 1, healer 1 makes a poor front line fighter type is not doing himself or his team any favors no matter what he claims to be trying to roleplay.
Can multiclassing be abused? Absolutely, but that's part of the GMs job, to rein in the guys who haunt the CharOps boards.
But if you can intelligently apply those choices to optimize your character for your campaign at your table
of course he's going to be more effective than a character who is optimized for some different set of circumstances. If he wasn't, what's the point of haveing options anyway?
If you mean that some PRCs are strictly, under all circumstances and for all purposes better than the base class... then I agree with you. Because that sets up a sub-optimization trap. Less severe than our Mt Dew sucking friend, but still a trap. There are, I think, only a few such PRCs out there. I suppose there shouldn't be any, but that 3e contains some mistakes across a couple of dozen books and a few thousand pages is no great shock and (IMHO) not rant worthy.
