I'm a mage, yeah. Mostly an elemental one, but I know bits and pieces of other things... even if most of the stories Merrill tells about me tend to involve me lighting things on fire.
Learning how to be a shapeshifter would give her more interesting stories to tell, wouldn't it? Like 'one time, Hawke turned into a mabari!' instead of 'one time, Hawke set a Darkspawn on fire and used it as a campfire!'.