Quote Originally Posted by chidarake View Post
The only time I cancel for firestarter is when I have already started casting blizzard 3 to replenish mp but the proc hadn't appeared before hand.

The obvious reason being the fire 3 will be under astral fire and if I waited till after blizzard 3 I may have to wait on mp tick to use it.

However I do also sometimes keep them depending on if its a boss because I will usually reapply lightning after blizzard whilst I wait on the mp tick assuming its not instant.
I can't imagine this hasn't been addressed yet, but rather than interrupting b3, finish casting it, do your umbral phase, and then rather than blowing firestarter from u3 hit transpose. Then you are starting your astral phase with an A1 instant cast fire 3.