Playing on hard I found it was easier going on the offensive and using Elize/Jude Recover Heal Link Arte when the buff wore off or I needed healing (didn't have dispel). Other than that I just pummeled and snap pivoted him to death.
The blue exclamation point that appears before they counter your offensive makes it easier to time snap pivot then just keep beating him. I died a couple times but after I got better at timing snap pivot I destroyed him. Using igneous crush whenever you can also helps with damage a lot.
This was also before I had access to earth weapons since I was saving materials for x3 bonuses.
I spammed the Jude x Milla Link Artes Runation Fangs. On Hard difficulty it took about 9? To kill the butterfly, pretty easy fight. Oh right, try to scatter out, this boss actually took 2 attempts for me since on my 1st attempt, the damned AIs all stacked on top of me and the Bell skill the butterfly used pretty much AOE wiped my party.
No the only way to be 100% Immune is via Korona Symbols the immunity skills only prevent it half of the time and with the RNG hating me in games its the other 50% of the time that hates me when a boss poisons the entire party at once while under status immunity skills being used.