Don't know if you have used the Unreal Engine, but I used to make maps for it all the time.
The way that engine worked is, the same I would assume as the engine WoW designers use.
Everything is in layers, the base terrain layer, which is a base color or design for the terrain. It's normally pretty simple, ranging from plain looking dirt to rocky, and gravel texture designs. With a huge number of variations and combinations. You can even combine multiple terrains for a multilayer look. If you assign everything by layers, you can even remove and reapply just that layer or change just that layer. Makes it very easy to change things even after you have the whole map almost finished.
The way the brushes work, are completely customizable. You can make them apply thick layers of a texture or a spread out thin layers. Over a small or very large area. So making a dirt road with rock and them maybe some pits and a few random patches of grass only takes a few clicks and a couple seconds.
You can do the same with bushes, trees etc.
Not to mention it's extremely easy to import you own textures and apply them to whatever you want.
I always just assumed most editors where made this way, or similar as it's extremely powerful, very flexible, and anyone can use it to make decent looking levels. Get someone with experience and you can make outstanding looking levels, in no time at all.
Re: WoW's secret sauce: tools
Don't know if you have used the Unreal Engine, but I used to make maps for it all the time.
The way that engine worked is, the same I would assume as the engine WoW designers use.
Everything is in layers, the base terrain layer, which is a base color or design for the terrain. It's normally pretty simple, ranging from plain looking dirt to rocky, and gravel texture designs. With a huge number of variations and combinations. You can even combine multiple terrains for a multilayer look. If you assign everything by layers, you can even remove and reapply just that layer or change just that layer. Makes it very easy to change things even after you have the whole map almost finished.
The way the brushes work, are completely customizable. You can make them apply thick layers of a texture or a spread out thin layers. Over a small or very large area. So making a dirt road with rock and them maybe some pits and a few random patches of grass only takes a few clicks and a couple seconds.
You can do the same with bushes, trees etc.
Not to mention it's extremely easy to import you own textures and apply them to whatever you want.
I always just assumed most editors where made this way, or similar as it's extremely powerful, very flexible, and anyone can use it to make decent looking levels. Get someone with experience and you can make outstanding looking levels, in no time at all.