I use them as individuals, but I keep seeing comments on the forums indicating others use them as a horde enemy.
My players mow through them at a good rate as it is, using them as a horde seems crazy. The new weapon stats, as yet untested, should hopefully make things more balanced for my group, but the idea of 60 Fire Warriors running together a pack doesn't sit with me.
They have squads of 12 in the setting/tabletop, are disciplined soldiers and operate in the field as a greater force... why would they clump together and charge the enemy, when squads spreading out makes more sense to control the kill zone.
So, do you use them as hordes or individuals and how do you find they work in game?