Based on Velanna's Keeper specialization (since sadly wasn't available for Lavellan this game!
) and Morrigan mentioning that some Dalish Clans have shapeshifting abilities similar to her own, it sounds like the Dalish have more nature-oriented magic. I imagine they also have more practical magic for everyday use, not just Ivory Tower Academia.
I thought that was a retcon at first too, because the Dalish were said not to fear magic and cherished their mages. Doesn't sound like it if they are sending them away to go die. But if you think about it, it does make sense...
No, it's a retcon.
Merrill said in DA2 that the Dalish believe all elves used to be magical, and that elves losing their magic is another sign of losing their heritage; that the Dalish value magic and want to encourage magical births because regaining their magic means regaining their lost heritage. She also said there have been fewer magical births in recent generations, so most Dalish have trouble finding enough mages to have even a Keeper's First; and that they have to trade mages between clans so every clan can have at least a Keeper and Keeper's First (never mind Second or extra).
Even in DAO, while they didn't mention any shortage of mages (maybe it's not an issue for Zathrien's Clan?), the Dalish still took two city elf mages despite having plenty of Dalish-born mages of their own, and didn't seem to mind having extra mages running around. Lanaya, a city elf who joined the Dalish in late childhood, said she had to compete with many Dalish-born mages to become Zathrien's First. They also took in Aneirin, a Circle runaway, and there was no mention of him being a Keeper's Second.
Then DAI rolls around and suddenly all Dalish Clans have plenty of mages to go around, and they all only want three per clan and will all kick out any extras, even banishing children to die in the woods? (And it's common enough that the Inquisitor can meet Minaeve and "Dalish," two different elves from different clans and backgrounds.)
I call retcon!
I like that you had the opportunity as a Dalish character to reply that your clan didn't do that, which hearkens back to the very fractured and balkanized state of Dalish cultural practice in the diaspora.
Honestly, I also felt like Minaeve's story was added to undermine a Dalish or Vashoth Inquisitor's empirical objection to Vivienne's "Circles are the only solution" claim, making it clear that Circle policies are not exclusively based in Chantry doctrine. It's a small part of what makes me feel like the writing tilts a bit against mage freedom in DA:I, along with things like Fiona's incompetence and the lack of a strong voice from within the Circle institution who argues against Vivienne's depiction of it.
I think that's what it is too.