Speaking for myself, if I want to try some particular multi-class build, I would want to derive some benefit from doing it. Likewise, if on another occasion my preference is to try some particular pure build, then I would also want to be able to derive some benefit from that, as well.
For example, if I want to get the most out of a swf fighter, I might find value in splashing some bard for swashbuckling. Since I'll be using light or no armor anyway, I might also find two levels of rogue to be valuable. People splash a some levels of fvs onto a cleric if they want a toon that can make good use of the cleric SLA boosted with the fvs enhancements.
So it's obviously okay for multi-classing to help. But does this mean that every "best thing" needs to come from multi-classing? I say no. It's fine for pure classes to be good, too.
Again, I have to wonder with the fixation on "killing off" some aspect of the game. Let's not kill off either method.