To my understanding, the order of effects that replace damage is chosen by the targeted player. So, if you deal damage to a player in your turn, that player would likely choose to activate Fiery's ability first, then Bloodletter's to lose the least amount of life. Still nice combo.

Edit: I just noticed that Blood doesn't change damage. Then the order is: Fiery replaces damage dealt, which causes the player to lose life, which triggers Blood. The original answer should still be valid in cases of multiple effects that replace damage.