As an RPer who was initially skeptical of Goblin Shaman, and someone who is now going to roll with, I'll explain how I will play my Shaman and my justifications for it:
As the Cataclysm happens, shaman become very important people; they're essentially the glue holding the world together. Goblins experience the rage of the elements first hand. This sort of power was just too good to pass up, and so they latch onto it, and learn to exploit it. Exploit
being a keyword here: Just because Thrall reveres the elements doesn't mean that all shaman necessarily have to.
People have already brought up the Taunka, and the Goblins seem to follow the same pattern. If you go to the Goblin Slums in Orgrimmar, you can go find the Goblin Shaman trainer standing by the pond. Her title is Elemental Engineer, and she is running an oil pump, forcing a bunch of little earth elementals to put oil into barrels and drag them ashore. She is not being nice to them at all, and spends some time yelling at them to pick up the pace.
You may believe that elementals are too strong to be enslaved, but the lore doesn't support that viewpoint. Obviously they're not running around with enslaved Elemental Lords
, but who is to say that minor elementals are more powerful than, say, Warlock demons? Goblins found a system to control elementals, both for power and cheap labor. Even the Elemental Lords were enslaved by Old Gods, after all.
Now, on to another point: Goblins are seriously getting a bad rap from people that isn't necessarily true. Yes, Goblins value money and profit, but that isn't their only motivation (at least for most Goblins). The Warcraft RPG actually pointed out that Goblins are fiercely loyal to their friends and customers:
Goblins are not purely mercenary. They are known to form strong bonds with individuals of other races. Their small forms and odd behavior make other races — elves in particular — ill at ease, but goblins do not seem to care much for the impression they make. They judge by deeds, befriending those who treat them as friends and standing apart from those who would offer them abuse.
Keep in mind that much of their culture comes out of them having been enslaved by the trolls. They do value money, as they see money as equivalent to power, and power as a way to keep from being exploited. They also value innovation, not just in terms of engineering, but in anything that interests them. Much like the Gnomes, they are often pigeon holed as engineers, but both can become obsessed over just about anything (Breeani excels at pet-keeping, and there is a Gnome in WotLK that has rejected technology and is essentially a hunter). That is why you see so many Goblin chefs, it is something where they can demonstrate a lot of creativity in, and make innovative new recipes, which in turn gets them profit.
Goblins are not as one dimensional as they initially seem, nor are shaman. If Blizzard's lore explanations don't fit for you character, follow a different path; just keep it reasonable.