You've been doing low-level DR around the holidays, when many new players are starting up. If DR is designed to fill in existing parties that are waiting for members, it makes sense that you'd see a lot of Sastasha and Copperbell up front. New characters coming up may be setting the tune for what DR is providing us.

I've also seen Halitali via low-level DR. Yesterday I saw the Ifrit primal fight (normal) as part of a DR group. I think things will get more random over time.