One thing to consider when choosing glyphs is that, at least for me, these days we clear ICC so fast that a Fire Elemental on 10 min CD would only make it available for every other fight.
You could probably optimize it by swapping glyphs during the instance if you want to keep swapping back and forth.

@ Izyy:

I did 10 runs through a simulator for each glyph set I was curious about. I then averaged the totals.
I loaded my little shaman in from the armory, set the fictional fight for 5 min duration, and changed nothing on each run but which glyphs were in use. Typical raid buffs, food & flasks were included in the calcs.
(Shaman is ~ 5850gs)

TOW/Ltng/Ft -- Average: 8915.48
TOW/Ltng/E.Mast -- Average: 8861.18
TOW/Ltng/Lava -- Average: 8933.94 <----
TOW/Ltng/Flameshock -- Average: 8876.58
E.Mas/Ltng/Lava -- Average: 8819.52
FT/Ltng/Lava -- Average: 8865.87
Flameshock/Ltng/Lava -- Average: 8854.08

Best three glyphs I've been able to come up with are Totem of Wrath, Lightning Bolt, Lava. If anyone has similar, differing, or more detailed info, I'd *really* like to see it. My testing was as good as I could get it, but I'm sure there are better.

Edit: What I was looking to find out is if the Elemental Mastery glyph was any good added to the T10 2pc bonus, with constant use. From what I can tell, that glyph sucks.

In addition, you can refer to this page from Zamir's blog about glyph choices since the 3.3.3 patch:

http://wowhats.wordpress.com/2010/03...s-flametongue/

This page is a great report on the argument whether to use Glyph of Flametongue or Glyph of Lava. According to your report, it does confirm Zamir's theorycrafting arguing that Glyph of Flametongue and Glyph of Lava are close competitors for maximum DPS.