(Commentary): Unit Exacitor is uncertain if the term, ‘evolve,’ was used to indicate that the Blood Elves themselves have biologically changed, or if it were a term regarding their lore and story changing. The wording was not particularly specific. That having been said, for the sake of discussion, I would like to speculative on the nature of this, ‘evolution,’ from a potential biological point of view.
(Speculative): It’s plausible that the Blood Elves’ efforts to combat the effects of withdrawal did result in a metaphysical alteration to what they are on a fundamental level. It would not surprise me if, say, by draining mana from other creatures, they’ve augmented their ability to possess mana efficiently without the worry of deforming into a Wretched. The magic draining technique could’ve slowly over time increased their tolerance to higher reserves of magic, and the Sunwell essentially now makes it possible for them to no longer be at risk of becoming wretched. This even sets them aside from High Elves on a metaphysical-biological level, as we’ve seen High Elves, even after the Sunwell was restored, can still become Wretched, such as the lodge in the Eastern Plaguelands.
(Conclusion): In Unit Exacitor’s speculation, by whatever combination of circumstances, the Blood Elves’ potential, ‘evolution,’ would be one that makes them superior to High Elves in the matters of magic.