You could keep all those powers as reactions by instead saying they heal you by the amount that normally would have been reduced, but that leads to its own set of potential issues:
1) If the original damage would have put you below 0, you would get extra healing since you would first go back to 0 and then heal
2) The powers would all be boosted by items and effects that increase healing gained.
3) They would also be negated by effects that prevent healing (ex: Clay Golem's Slam attack, or the aura of a Klurichir
3) Any effects that trigger on becoming bloodied or reaching 0 hp would trigger before the healing occurs.
Personally, I don't have an issue with a reaction type power reducing damage taken, even if its not called out in the immediate reaction rules as a specific case that breaks the general rule of resolving after the triggering effect, simply because its clearly RAI to make those powers work, and avoids the complications I listed above.