I think that Humans are very keen on magics, and have a great proficiency in magics as their thing. They're essentially power sponges, but not like Elved that just absorb magical energies. So yeah, there is no reason that Humans couldn't be Druid, or Shaman by what you stated previously about being around teachers for years now. Going back to Arathi Highlands, once a great Human hub, it is covered with tons of Elemental zones. There's no real reason that they couldn't have gotten into Elemental commune then.
As for Gnomes, while they are painted at being highly intelligent, I'm going to agree with Saltysquidoon about Gnomes being Druids or Shamans. They are intelligent and proficient with Magic, in that Arcane magic is supposed to be pure mathematics in the Warcraft universe. They do not have any real connection, or desire to push for natural understanding.
If Stormwind Humans could become Druids, or Shaman as well, they could canonically fix up Westfall of the elemental destruction and nourish the land to be a verdant, farming haven. The refugees would no longer be homeless.