I have to admit, the inclusion of such things as Duskblade and the like make me go yuk. would people be content to see these as Prestige Classes however?
No, I would not be content with that at all. For one thing, that would entail a return to the 3E multiclassing and prestige class system, which I hope we can avoid. More important, though, is that the Duskblade is a great idea for a main class, has previously existed as a main class, and by this thread is clearly popular as such.
I see no reason whatsoever to relegate such a cool class to being a secondary option, simply because it makes you say "yuk". You've got to admit, that is rather petty and selfish on your part. You could at least provide some justification for your dislike so we can discuss it properly.
Everytime they formalize a character concept that concept is somehow barred from the imagnation. "My fighter is a mercenary. No, not the subclass mercenary nor the prestige class mercenary. He's a mercenary in that he fights for money, he is just bad news. No, he does not have the mercenary issue eye-patch with +2 intimidate bonus from page 72 in The Book of All Fighter Stereotypes but he does have an eye-patch. See?"
This is only really true for really bad class design, and doesn't work when generalized out as a complaint against having more classes.
Sure, if you design a class called the Mercenary, and its concept begins and ends with "it's a mercenary that fights for money", then it is a bad class for a hundred reasons beyond your complaint. I don't want that kind of class in D&D and I'm the guy who wants a hundred classes.
Classes should create new mechanical options. They should make character concepts that are impossible with the existing rules and classes into possibilities. They should fill roles that have not been done before and create new opportunities for players to express their imagination in novel ways. This is why they should exist to create entirely new mechanics that can be flavored in many ways (as with many good classes), rather than be attempts to straightjacket flavor to poorly executed and dull mechanics (like in your example).
Overall, there are so many things that D&D simply
has never done with its classes that we are very, very far from the point where we need to worry about well-designed classes stepping on each other's concepts and limiting player imagination.