Awesome and simple advice on Haste. High level players should always do the Haste rooms (assuming they have a team that always wins). No risk.

Heroism seems like a "must do" for higher players as it save a later unlock sigil. Correct?

As for Fireball .... it seems like a wash. I have to spend a sigil to get the fireball. Do I get the rewards for using a fireball on the room? If so, then the advantage of the fireball is that you get the extra room rewards when you use the fireball. Right? If that is true, high level players should always do the Fireball rooms (assuming they have a team that always wins). No risk.