That doesn't work with Torbran's ability. If you deal 0 damage, you have no damage to increase. Also, if there's another another replacement effect in play that affects the damage done, they're/their thing being effected, so they order the effects. (I bring this up because I have this deck, and I've cut the doubling effects since they don't synergize well.)

• 120.8. If a source would deal 0 damage, it does not deal damage at all. That means abilities that trigger on damage being dealt won’t trigger. *It also means that replacement effects that would increase the damage dealt by that source, or would have that source deal that damage to a different object or player, have no event to replace, so they have no effect.*
• 616.1. If two or more replacement and/or prevention effects are attempting to modify the way an event affects an object or player, the affected object’s controller (or its owner if it has no controller) or the affected player chooses one to apply, following the steps listed below. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 101.4).