Healing parses are largely irrelevant in my opinion. Other than checking you haven’t got a healer sat there doing absolutely nothing the whole fight. There are too many factors that can positively, or negatively impact healing logs.
Just a few quick examples and there is a lot more, if your raid group doesn’t take much damage, it’s incredibly hard to parse well as there isn’t much to heal, you’re competing with 8+ other healers for the little healing that is required = lower hps. If your raid group takes lots of damage, it’s incredibly easy to parse well as there is more to heal = higher hps. If you’re a raid healer rather than a tank prio healer, it’s far easier to parse well. If you fudge the meters by healing the warlocks when they’re life tapping, it’s far easier to parse well.
Yes, they can give an ‘indication’ of whether someone is doing the right things, and fine if you’re just using them as a bit of fun competition between yourself and your guild mates, but as a world wide comparison, there is just too much that influences healing parses for them to be considered a reliable result. Every raid group/guild is going to be different in terms of how many of your raid group will avoid damage correctly (as they should be), how much damage the tanks are taking (if they’re using cool downs on certain encounters etc)