We had three paladins chain casting downranked holy lights on the tanks for our Brutallus kill.
WWS shows the "raw" healing, that is, the total heal output, for all three paladins to be about the same. The "effective" healing, that is, the amount of useful healing, was drastically different, with one paladin (call him "bottom") being at almost half of the top paladin, and the second paladin being in the middle (call him "mid").
The combat log showed that for much of the fight, the 3 paladins were casting in lock step, with the top paladin's HL landing, followed very shortly after by the mid paladin, and lastly by the bottom paladin -- resulting in the bottom paladin's heal being almost entirely overheal (WWS report overheal close to 70%).
Holy light, with "Light's Grace" up, is a 2 second cast, which means it would be tricky for the 3 of them to manually spread out thier casts. Ideally we would want them all landing about 0.5s apart. Are there any cast bar mods that would help coordinate this?
Alternatively, I suppose we could have all 3 of the downrank even more...