Doedre's Undoing does not benefit from Hazard bonuses or Triggered Spell bonuses.

There's already been a bunch of reports about Rearming not working, but to add to that:

+50% Hazard Area of Effect (Widespread Coverage notable) does not do anything for the support, aoe remains the exact same

Damage seems to stay the same with any additional Hazard Damage or Triggered Spell damage added in. However, oddly enough, the Notable "Dynamism" which gives "40% increased damage on triggering a skill recently" counts for increasing the damage, meaning it is a triggered skill that does spell damage, but doesn't benefit from Triggered Spell Damage.