My suggestions:

-Make thunderhead buff 40/45s like thunder 3 used to be, having a 30s dot tied to a 30s buff is a really bad design.

-Bring enhance flare back and increase high fire/blizzard potency for aoe. Aoe right now is extremely bad.

-Make flare star instant and maybe refresh AF timer, it should feel like a reward for doing your fire phase properly, instead it feels like a burden, also let us carry the stacks in umbral ice and give us an option to use it with less stacks with lower potency for downtime, fuck ups, or shorter fire phases.

I believe with these 3 changes BLM would be in a fantastic spot.