Since the Holy Legendary I want is from the raid's last boss, I went ahead and made this one
and I'm not sure if this is a common misconception or I'm just an idiot (and a friend of mine who assumed the same) but this legendary is actually a lot better than I thought it would be. As I read it I assumed the idea was get 5 stacks using Flash Heal and your next Heal has a faster cast + increased healing, but it's not the next Heal, well, it's not JUST the next Heal, the effect persists as long as you have the buff up (which lasts 15 seconds and is refreshed everytime you flash heal).
So as long as you can keep the buff up, you have a 1.x (.x cause of haste) second cast Heal with 15% increased healing.
and I'm not sure if this is a common misconception or I'm just an idiot (and a friend of mine who assumed the same) but this legendary is actually a lot better than I thought it would be. As I read it I assumed the idea was get 5 stacks using Flash Heal and your next Heal has a faster cast + increased healing, but it's not the next Heal, well, it's not JUST the next Heal, the effect persists as long as you have the buff up (which lasts 15 seconds and is refreshed everytime you flash heal).
So as long as you can keep the buff up, you have a 1.x (.x cause of haste) second cast Heal with 15% increased healing.