So numerous references are made to both heaven and hell in WoW.
- Uther telling Arthas to go to hell.
- Sylvanas being tortured in hell after she commits suicide.
- The quest in Icecrown where you help the solider and eventually the light takes him.
Ultimately everything we see in WoW that's energy based is derived from some iteration of a plane, so based on what we know one would assume that heaven is a plane of light and hell is a plane of shadow or void. (With the exception of several species who have their own "rules" such as Vrykul culture)
Does this mean there is one ultimate being ruling over these planes, al a Ragnaros or Al'Akir - essentially leading to a God and Satan type character within the light and the void.
The Pantheon are essentially our creators and created everything we know, so there is a disconnection between a creator such as god and the deity of good.