I've posted this on the WoW forums too, but I'm anticipating the usual responses of 'why aren't you playing disc' or other mongoloid remarks, so I thought I'd post here.
So before the new season starts I'd like to make a decision regarding glyphs. It seems to me there are lots of glyphs which have potential, and choosing between them is hard.
A note: my thoughts regarding #1, #2 and #3 are aimed primarily at melee-based teams who will most likely at some point want to train me. I am of course not planning to use the same setup for every match.
1) Glyph of Shadow Magic. To lots of people this would be a no brainer (to those who don't know, can't remember, it provides 5 sec immunity to silence/interrupt when casting fade, 1.5 min CD). But I'm really not sure. Firstly any half decent player will be able to prevent you from casting through it regardless by stunning, gouging, death gripping or whatever they can do (assuming they're on you. Mage/warlock teams might be a different issue). Secondly, standing still and casting while receiving damage isn't ideal. And the CD is long.
2) Glyph of Fade (-10% damage when fade is cast, 30 sec CD). Obviously this can't be used with the previous one. I'm thinking this might actually be superior to shadow magic; 10% is a lot of damage prevention, and would probably equal the damage you'd have healed up with shadow magic anyway. And its CD is a third of the previous one.
3) Glyph of Levitate (+15% movement speed during Levitate, and for 10 secs afterwards). Have I gone mad? Perhaps. But I'm thinking this might actually be a good option if taken alongside the phantasm talent, whose major drawback is that it doesn't increase your movement speed at all. Assuming you have some peeling, this combination should allow you to get away from anything. The drawback of course is that you would have to sacrifice angelic feather; hence it would obviously only be taken when you're facing a melee cleave, or a team likely to nuke you.
4) Glyph of Guardian Spirit (+200% healing received by target of GS, but no longer prevents death). 260% is a LOT. I don't find the death-heal to be too reliable anyway, I sometimes find myself having to choose between letting the target 'die' to receive the 40% heal, or healing them up in fear that it might expire. Torn on this one.
Those, for me, are the debatable ones and I'd be interested to hear people's thoughts. Obviously glyphs like Inquisitor, Mass Dispel, Renew, Fear Ward, and Smite are all mandatory in certain situations, but those situations are usually fairly obvious.