I've been running [Glyph of Holy Wrath] for the last couple of months. Originally, it was for Ragnaros, to add extra stuns on the Sons of Flame.
But it turns out that there are a lot of other places you can use Holy Wrath and get off a short stun, especially in Firelands. This glyph is turning out to be quite enjoyable. I'm rather glad that Ragnaros provides an excuse to take this glyph instead of the more pure healing choices.
My current favorite place to use the Holy Wrath stun is Heroic Ryolith. The little blobs that move towards Ryolith and increase his armor when they fuse are elementals. So you're busy healing, and you notice that a pack of blobs are moving past you towards Ryolith. A quick Holy Wrath, they're all stunned, and that delays the increase to Ryolith's armor, theoretically speeding up the kill. Realistically, it probably doesn't make a huge difference, but I enjoy stunning the blobs, so I'll pretend it's vital for the kill.
You can also stun the regular elemental adds, but that's less interesting.
There are a lot of other places where the AoE stun can be used. It's especially easy for a healer to use, because you don't have to change targets, you just have to be close by the mobs.
So, [Glyph of Holy Wrath]. A surprisingly fun and useful little glyph.