Yeah, I know everything WotC isn't all that balanced and stuff, but with core and the completes, barring Wizard/Cleric/Druid20, there's not a lot you can multiclass into and do what I described above.
I tend to stick closely to core. As you say, if you figure out how to handle Wizard/Cleric/Druid/Sorcerer, there isn't alot that is breakable in core. Granted, you do need to nerf the big four a little and bump up a bit in power the rest, but I don't need 600 classes which badly accomplish that purpose to achieve those ends.
The same guy who made that character for my game made a "Blue mage," for those who don't know, it's a sex mage...
Ahh... yes. That's about the actual point where I start worrying about obscenities and crudeness in the game.
But after him, I'm banning all GR products and any 3PP unless I've played it or seen what it can do.
That's a sound policy in my opinion. Failing or not on my part, I couldnt' even keep up with all the WotC options - either economicly (buy al l those books) or mentally (memorize all those class entries). And I did want to use the GR material, because while there was alot of poorly thought out material out there, GR in particular I thought was doing more flavorful and interesting stuff than WotC was.
One of the reasons why 600 classes is bad is that I don't want to have to poor over the rules to discover amongst the 360,000+ combinations which ones can be dipped effectively to synergize up something breaking, nor for that matter do I want to force my players to do that. And above all, I don't want to have to spend that much time prepping NPC's.
There are some legtimate problems that PrCs were leveraged to address, but they were never really meant to address those problems and in most cases did it quite badly.
Legitimate Problems:
a) From the core, certain archetypes - swashbuckler, champion of evil, arcane necromancer, military leader, urban tracker, etc. - simply lack a good mechanical representation.
b) Multiclassing doesn't really work as a means of hybridizing a spellcasting class.
c) From the core, full spellcasters complete outstrip the power of the other classes beginning around 12th level (some say even sooner, and I feel no need to quibble).
Reasons Why PrCs Don't Work as Solutions
a1) By trying to provide those archetypes via a PrC, you are essentially saying, "You can't really be your concept from 1st level."
a2) You are also creating an inflexible solution that isn't really built for customizing. PrCs usually have very tightly defined progressions - you get X at 1st level, Y at 3rd level, Z at 6th level. So to get 'Z' if 'Z' is what you really want, you not only have to pick up the baggage of X and Y (which may not fit), but you have to pick up all the baggage required to qualify for the PrC.
a3) The only way to achieve the flexibility that players were craving was to keep providing more and more mechanical variation. But that has the problem of unintended synergies, to say nothing of rules bloat and putting a time burden on the DM when it comes to creating NPC's.
b) The concept of PrC classes designed to enable spellcaster multiclassing in a general sense does address the problem, allowing for you to exchange a few levels of crucial spellcasting ability for a comparitively large slice of class abilities from the other class. The problem is that by using PrC's, you essentially have to have a PrC for each class synergy you want to facillitate. So you need a rogue-wizard, fighter-wizard, ranger-wizard, monk-wizard, fighter-cleric, bard-cleric, ranger-cleric, rogue-cleric, monk-cleric, wizard-cleric, barbarian-druid, ranger-druid, fighter-druid, rogue-druid, and so on and on.
c1) Attempting to use PrC's to balance the game was inherently flawed on several grounds. First of all, by introducing 600 PrC's, you were essentially throwing play testing out the window. There was no hope of even getting all those classes reviewed by an editor, much less playtested.
c2) As a side effect of 'C1', PrC power levels were all over the board - from much weaker than base classes to much much more powerful than them.
c3) To actually address the problem would have meant lots of martial enabling classes and no worthwhile spellcaster PrC's. But of course, they didn't actually do that. The result was that as powerful as Wizard, Cleric, or Druid already was, there were Uber-Wizard, Uber-Cleric, and Uber-Druids available as well as tons of classes you could take to give up nothing and get something extra on top of your spellcasting ability. So in order to keep up with the new caster PrC's, they had to make even more powerful and breakable abilities for the martials. But then, they had to print new PrC's for the fans of casters, and these presented new oppurtunities to break the game, and so forth. But that meant that old material wasn't balanced with the new material. CR's of older monsters didn't match those of newer ones. Nothing was portable, and the better the customer was, the more likely it was that he was getting completely frustrated.
Way back when I first started playing 3e (2002?) I was trying to convert I3

yramid over to the new edition, and I got stuck trying to convert the Dervishes and other monster entries. They very much wanted to be barbarians, but they were lawful. And they had features that suggested variations on the Barbarian that weren't available in the rules at that time. "Aha!", I said to myself, "I'll create a PrC. This is exactly what PrC's were designed for. It's a secret society with unique abilities." So, I did. But it never really worked right; it was good, but I'd had to make comprimises in the design and in the faithfulness of the adaptation. Had I just been running it for myself, I'd have used Rule 0 and ran with it. But I took some additional effort and published it to EnWorld, and the more I thought about it, the more I realized that the problem wasn't fixable with a PrC. It was only fixable by fixing the Barbarian class. Thus, the Fanatic class was born (and evolved from its simple orgins as I encountered new ideas), and the decision was made to ban PrC's.
I've never regretted it. I use to run pickup games at tables weekly for the local gaming store, and I got to watch PrC's in action and that only reinforced my decision.