That fight was a delight, though visually hilarious on a BLM. Sadu and I, both standing there, casting at each other's face. Potions were used. Manaward was used off cooldown. I may have used Drain once or twice. I skipped through the meadow with Sadu chasing me whenever Triplecast was on. I had to hear that killing the adds drained her HP from someone else because it all happened so fast for me. My biggest regret, truly, is that I will not be able to experience it unless I play through the story again, and no other chara I have mains BLM. Sadface.

As for difficulty, some of my friends needed several attempts to clear it, but they got there eventually as they learned the fight and planned their actions. The one that took the longest was a victim to the bug where Sadu would become invulnerable at 1% and the duty would fail, which persisted even after they reported to have fixed it. He got it eventually, though.
And now, I wonder, if OP wasn't victim to that as well. Which is an entire different can of worms that can be debated, how every patch in recent memory has some progression breaking bug or issue to it.