Sorry, but I am going to have to disagree on Amplify magic. On most fights, this is a boon to your healers to put on the tank. The spell functions as if the caster had that much additional Spell Power. That means that if you put it on a tank, it's like all the healers have an extra 255 Spell Power. That's not a small number, and talented, it can be as much as a 10% increase to the healer's effective spell power. And when you consider the size of the spell damage the tanks take, the negative impact is pretty minor: IE, 10000 damage Lava Blast vs 10250 damage Lava Blast. The increase in mana efficiency quickly overtakes the disadvantage.

Moreover, in an attempt to keep Dampen magic from being too powerful, many of the DoT like ticks are not affected by (D)amp magic. So, when you fight Hodir, you can feel free to toss this on everyone in the raid to make those Prayers of Mending, Circles of Healing, and Wild Growths hit for a little bit more with no downside.

Also, ever try Dampen magic in PvP? Very helpful.

Sure, Amplify magic isn't great all the time. Never put it on the add tanks for ignis, because it makes the fire tick for more. However, it's not the worthless spell you make it out to be. It's actually one of the most unique and useful buffs that mages bring, and one that directly helps the healers.

Mana shield not useful in PvP? That's practically the only time I use mana shield. If my healer is CC'ed or dead, I need emergency buttons like that to keep myself alive.

Anyone remember Orangemarmalade's tournament game where he combined a stolen power word shield with a mana shield to successfully take down two full-health enemies, all while being alone with only 700 hit points?