In this order, you build on the idea of Dreadwyrm Trance, introducing the base mechanic, then the interaction with Ruin III, and finally Deathflare.
Again, with how MP hungry the spell is, there are so few situations when Ruin III outside of Dreadwyrm Trance isn't harmful. Dreadwyrm Trance effectively unlocks Ruin III and makes it useful, but Dreadwyrm Trance is useful outside of Ruin III. Ruin III is not realistically useful outside of Dreadwyrm Trance.