The glyph was useful when we were on fights with a lot more spread healing and when mana was a lot tighter, but right now with the new 4p and High Tide it is not really worth it. You want to be able to spam it for some periods, Ascendance being a big part of this.
I could see the glyph being somewhat useful on Iron Reaver and maybe Socrethar, but it all comes down to how well people position. If your raid is spread the fuck out it will be beneficial, if they have brains and stand appropriately you should leave the glyph. It will also make it easier to push out a bit more mana when you have the freedom of spamming chain heal.