This is the part where I brag about getting the Jaws of Defeat. Note that it is an on-use trinket, as follows:
Use: Your next 10 spells cast within 20 sec will reduce the cost of your holy and nature spells by 110, stacking up to 10 times. (2 Min Cooldown)
Ok… in order to get the most out of this trinket, you want to cast 10 spells in the next 20 seconds. This might be hard to pull off if you’re not spamming your 1.5 second heal or casting instants on the GCD.
For the Discipline Priest
Infuses the target with power, increasing spell casting speed by 20% and reducing the mana cost of all spells by 20%. Lasts 15 sec. (2 min cooldown)
So… a haste buff so I can squeeze more spells into the 20 second window? Yes please! Also, note that both spells have the same 2 minute cooldown (and a close duration). It’s quite easy to macro those suckers together.
For the Alchemist
Uses your skill in Herbalism to absorb energy and nutrients from the earth, instantly healing minor wounds and granting 480 haste rating for 20 sec. (2 min cooldown).
This is basically the same reasoning behind macroing with power infusion. A haste boost allows you to cast more spells, ideally hitting 10 within 20 seconds. The cooldowns also line up with both being 2 minutes.
For the Resto Druid
Shapeshift into the tree of life, increasing healing done by 15% and increasing your armor by 120%. Also protects the caster from Polymorph effects. In addition, some of your spells are temporarily enhanced while shapeshifted. Lasts 25 sec. Enhanced spells: Lifebloom, Wild Growth, Regrowth, Entangling Roots, Wrath. (3 min cooldown)
Now, when you hit Tree of Life, you’re spamming all the things. Lifebloom multiple targets, instant regrowth, etc. What’s not to like about a reduced mana cost for the spam-frenzy? Now, the cooldowns don’t quite line up, but it might be worth delaying triggering the Jaws until you trigger Tree of Life.