The difference was probably one mage using raging strikes.

Anyways, BLM is pretty good stationary damage. It takes a hit in mobility but it's not always that bad because oftentimes you'll have a proc and scathe to weave in between movement.

The problem as was said already was the RNG nature and how Firestarter procs are so terribly designed where they will trigger when you are already in the middle of another Fire I cast.

Nevertheless, you have the best burst aoe dps in the game as BLM, you've got best burst tied with dragoon, and you've got really useful CC like Freeze and Sleep.

Honestly the only class I feel doesn't bring as much raid utility is Dragoon tbh.