I heard some talk about 'variant classes' and the topic under "New Users" gave me a hint about what it might be. Is there a topic somewhere that talks more closely about different variant classes that I could see? Or are the previous "prestige classes" now the variant classes?
The old "prestige classes", most of them, are simply considered "variants" these days. They are classes with further specialization or other gimmicks than the standard base classes, so to speak. So you can take a look at most of the old prestige classes and roll them up as base classes, with the exception of Demon Hunter, Dragonsworn and Felsworn that have special rules and need to be submitted through Private Discussion as Special Profiles.
... You also can't play any of the classes that are specifically "this class, but stronger" such as the Arch- classes.
The Variant system's basically in place to give you more creative freedom with your characters and their abilities and give you access to classes that weren't available before. Necromancers, for instance, who are a Mage variant.
I don't think there's a post anywhere specifically dealing with this, though.
A special post about this would clear out many questions, I'm pretty sure, but I guess we'll have to do without one until someone gets hurt.
EDIT:
I presume Ley Walkers are also prohibited?
Ley walkers are not prohibited. They are a variation of mage, that do magicky things through the ley lines.
I've always assumed that as long as you give a good reason why they've gone down the often extremely specialized path they've gone down, things are fine when it comes to variant classes. Variant classes aren't any stronger, just more specialized.
What landashua said, yes. As long as you can justify your abilities and make them believable within the limits of the system (nothing overpowered, unfitting of World of Warcraft lore, and no multiclassing), you can be pretty creative with your variants. Just look at the base class (the one you pick OOCly) and look at the abilities they have and go from there. Or pick one of the "classes" that are based on other things (by taking inspiration from old prestige classes, for example).
Be fair and creative. That's it.
To give you a hint of what all you can do/make up with the Variant System, I was able to make a "Tech-priest". That is, instead of a "tech-mage", I switched the mage part with a discipline priest. It's a little easier done with Cataclysm around, because I think it's mentioned in the lore of gnome priests. But, this was done when we were still on WotLK.
There's no real super-guide to this since it's not really a "system." It's our attempt at being more open to different concepts, ranging from characters using different methods to explain their class abilities, to trying off-beat classes that go in a different direction or offer limited hybridization. Trying to write a full, comprehensive guide on all of the possibilities would essentially defeat the purpose.
Bounty's guide offers good guidelines, of course, but in general we just try to be chill with things unless they're crazy OP or go against the established canon of what the world permits.