Do Flame Legion use their own gear?
You have to remember that the Flame Legion are outcasts. They have very little in the way of being able to be self sufficient. They need to raid and steal other peoples equipment.
Outcasts that have a capital citadel of Hrangmer, along with the Citadel of Flame. One could think that they would be able to forge good armor and such for themselves. But maybe it is only the Flame groups skulking around in Ascalon that need to steal their equipment.
In Fireheart Rise, they keep Grawl slaves to mine metal for their weapons. It’s part of a dynamic event. So they are self-sufficient, but they probably steal weapons/armor quite often as well—considering how often they raid the Black Citadel and other, smaller Allied Legion bases.