Easy enough to add a shaman, instead of a mage...
On the same account as where they shammy should have been...
With the next set you level up.

You are leveling a lot of combinations, during RAF.
And the leveling group doesn't necessarily need to be the playing group composition.

Plus, I've changed who is on the teams a few times.
Usually at or near the start of an expansion... when they've changed things, and it looks like these classes will work well together.