I think you got it wrong here. Shamans don't control fire or other elements in the sense that they directly call fire out of thin air. They gain those power by asking/demanding/making deals sentient beings called elemental spirits. The spirits give them access to the types of element they represent. Fire as natural force are just like arcane. It's not sentient being.Nelf shamanism would not be about spirits, just about the elements.
People fundamentally misunderstand the difference between Druidism and Shamanism. Nature in Druidism and Shamanism are not the same thing. I wouldn't even call Shamanism that it's about nature. They just use natural forces.
Shamanism is about communing with the spirits to gain access to all these elemental powers. Shamans act as mediator between spirit world and Azeroth. They get those power from those spirits through variety of mean. You will see that Shamans are able to shift into ghost wolf. The key word is "ghost" which means it is of spirit world. The ability defines the difference between Shamanism and Druidism. You could see that Thrall was powerless when Garrosh locked the spirits in that area away.
Druidism is about Azeroth itself. It's about waking,living and breathing world. Azeorth itself has its system of how things work. Druids tap into the system and through that knowledge they are able to mess with the system or balance it.
Ever wonder why Druids who go into Emerald Dream and sleep for many years become more powerful? Emerald Dream is the blue print of Azeroth. By "studying" there they learn the structure of Azeroth in its purest form thuse making them more connected to the ebb and flow of the waking world.
When Shamans call a storm, they ask spirit of the wind to lend the power. Druid can do the same thing but different mean. They do it by harnessing the power of the nature itself. They know how to manipulate the weather to create a terrible storm. They tap into "the code" of nature to shift into different life forms.