I just wanna doublecheck something (BLM)

[Karilyn]

I'm leveling a BLM (lv37 now) and was kicked from a Brayflox Longstop dungeon run because someone in the party who said he had an i94 BLM got angry at me; he said that if I cared about my DPS I would be using Fire II on packs of three or more mobs. I commented back that it was my understanding that unless there was 4 or more mobs, using single target attacks was higher DPS, and then he vote-kicked me from the group.

I'm about 90% certain he was wrong, but never let it be said I don't confirm things. How many mobs should there be before I start using Fire II?

EDIT: I'm torn between thinking this post is really stupid for even bothering, because the guy was pretty extraordinarily bad, and yet at the same time, I refuse to ever insist I can't learn something new, because that's how I stop getting better, and I am fairly new to BLM anyway and apparently the other two party members agreed with him, so maybe I am wrong?