Can anyone explain Well of Existence to me? (holy)

[Raetary]

It's supposedly one of the best essences for holy (or really any healer for that matter)
But isn't our thing that we DON'T want to overheal?

I can barely ever fill it up enough to be of any significance unless i waste a cooldown or 2 early in a boss fight.

[DechCJC]

At least for disc it's amazing. In a M+ environment, it's easy to radiance the group and just passively heal them whilst building up the well - I actually overheal on purpose through atonement so that i can deal with emergency spike damage, which is something that disc in particular is very bad at normally. I can heal a tank with over 400k hp from 20% to full in one cast with it quite easily, it's insanely good.

I don't know why it's good for other healers though, seems like you'd have to go out of your way to overheal in most cases.

[Atharaxie]

Holy tends to overheal in raid, much less in M+
Disc always overheal so Well is good in M+ but I suspect Ever Rising Tide is far better combo with atonement ramping in raid.
In M+ as Holy Lucid dream would be a good minor. As Major, Ever Rising Tide or Life Bender would probably be my choice.

[Echeyakee]

Well, you can't avoid overhealing, so it will tick up. Your CoH, trail of light and mastery will get some in regardless. Obviously if you're gearing for M+, you won't have much mastery, but it's just that. I did notice that I'm much more liberal with my serenity, as I know that I have a big heal available if shit hits the fan, so I tend to pop it earlier.