No you don't need to destroy the anemo pillar. The boss regens once regardless. That's the same thing with regular anemo hypostasis as well.

@Solcaihn: I had similar situation. The boss died only after I collected all orbs AND destroyed all crystals on ground. I think second part is a bug.

Don't listen to these monkeys, gathering the orbs in the air actually should worth of attention because each orb the boss ***orbs, his health gets regenerated as well, and since there is a time limit, you don't want that to happen.

It might just be that I'm blind and am missing some Anemo orbs when the boss breaks apart near the end, but I could swear I've gotten to that point twice, gathered all the orbs I could see, and it just kept reviving itself. Anyone else with similar problems?