So they do [exist]. That's what this new Inscription skill in LK is. So we find that there are a number of glyphs that a druid can use, including the Glyph o' Moonfire. Should we use it? Its sizable DoT bonus comes with a serious up-front penalty.
Increases the periodic damage of your Moonfire ability by 75%, but initial damage is decreased by 90%.
So here's the best looking comment from WoWhead.com:
As you can see - If you don't crit often, Moonfire with Glyph does more dmg. But if you're lucky for crits Moonfire without Glyph does more dmg.
Don'crit often? Are you kidding? Gimme that up front dmg, then.
Ah, but wait. Combine with another glyph and we're on to something, maybe.
... use glyphed Starfire to extend its duration indefinitely (with crit + haste you can land a Starfire every 2-2.5 seconds). Since you never have to reapply the DOT you can keep up the highest possible tick and won't miss the initial damage from the glyphed Moonfire.
I love Moonfiring the killshot. OH, BUT IT W4ZT3Z M4N4!!1! Yes, yes, I know. That's why my favorite comment in the thread about the Moonfire glyphs is this one...
A Boomkin spams Moonfire to finish off someone quickly. Yes, it does burn mana. But you see, the Boomkin can sit down and have a drink whilst sitting on the corpse of their enemy.
The /oom now so that we can drink later tends to be my attitude, the impatience of my PUG for whom I was going to try main healing as Balance spec nonwithstanding.
Still, I'm intrigued with the Moonfire glpyh. The Starfire glyph, however, is a no brainer. Let's go see how tough that is to get.
(Btw, if you're wondering why a panzerkin blog has so much general balance stuff, it's b/c DPS == panzerkin threat. What's good for the goose, given plenty of armor...)
EDIT: Icedragon weighs in that there is no infinite Moonfire extension now, just a 9 second buff if all goes well. So for my playstyle, at least, the Glyph of Moonfire is out.