Condi Firebrand only performs great in half of the fractals or raids.
What makes it Op is the bursty nature of the burn condition by itself. Make a burn condi tempest or weaver and will do the same.
I think is the right balance, high burty dps at the cost of low HP pool and being in melee range. I'm talking about axe, I dont consider scepter in a full burn build.
In addition, only works well against stationary bosses, others that move or teleport a lot are harder to make them eat all the burns.