Does the ongoing effect of a card effect only the hero using it, or all heroes?
Ex: Ra has a card that increases all Fire damage by one, and also changes the damage type of all heros to Fire. When this ongoing card is in play, does this essentially mean that all damage done by all other heroes is Fire+1 as long as the ongoing card is in play?
So with Imbued Fire, it changes all damage a hero deals to fire. It also increases all fire damage dealt, no matter if it's done by a hero, villain, or the environment.
Tempest's Otherworldly Resilience only provides DR to him. But Shielding Winds provides every hero with DR from instances of 5+ damage (that's a single instance of damage, so "5 (type) damage", not "five total damage from one source in a turn (1,3,1/2,2,1/3,2/1,1,1,1,1/etc.)"). However, Legacy's Superhuman Durability only reduces damage to him, as it specifies (but it provides more DR!).
If a card says "Increase all damage dealt by 1" then all damage is increased. Villain, hero, and environment; be it from a target, one-shot, or abstract source like "the environment". "Increase damage dealt by villain targets by 1", however, increases damage dealt by any villain card that has HP (as a target is a card with HP).