The Unkillable Angel

The idea is to build into Weapon Power and Ability Cooldown to boost the power of her damage output, but also have access to Resurrection as much as possible. Weapon Power will also boost the amount of healing she does, so that plays in nicely. Once you also acquire the Crepuscular Circle, it allows her to apply the healing and damage boost to players with no downside to getting her gun out and blasting. Eventually she will also get mini-Valkyries for resurrections too. This is just pure fun if you've ever wanted to actually play into the attack side of Mercy.