Insanity

See you all in Trollduar.

Hey, everybody, guess who's back. (Hint: it's me.) Unless you've been under a rock, you all know 5.2 is out. As patches go, this one's pretty glorious for Shadow priests. We've all been a little bit on the wimpy side through last tier, and the couple buffs we've gotten are quite welcome.

Shadow Buffs

• Insanity redesigned. Details below.
• Shadowform damage bonus increased to 25%, up from 20%.
• (Not yet live) Shadow Word: Pain damage increased 25%.
• Power Infusion now grants 5% damage while active, in addition to its previous effects.
• Shadowy Apparition pathing is noticeably improved, and the limit is increased to 10 at a time, up from 3. They still fail a lot, but it's a lot less.
• AoE target cap increased to 20. While this effects all classes, it will bring Shadow closer to specs that can apply DoTs in an AoE in very-many-target situations, and greatly increase the healing of Halo in 25man raids.

Shadow Nerfs

• From Darkness, Comes Light nerfed (to the ground, baby!) Proc rate much lower than tooltip listed rate. The Surge of Light portion can no-longer proc for Shadow.
• Healing from Flash Heal, Binding Heal, Renew and Prayer of Mending reduced to 80% of previous.
• Dispersion is a shadow spell, and can be locked by school interrupts. (This has already killed me a couple times in 5mans.)
• Glyph of Mind Spike is now worthless. (Further reducing the value of From Darkness, Comes Light.)

Mind Flay: apply directly to the forehead.

The New Insanity

As promised, let's talk about the new Insanity. The Solace and Insanity talent no-longer grants Shadow priests a spell. Instead, if you start a Mind Flay cast on a foe with your Devouring Plague on it, the cast morphs into Mind Flay (Insanity), dealing +33% damage per Shadow Orb spent. It's an entirely different spell, but I couldn't find it on Wowhead to link it. This bonus damage persists for the duration of the channel, potentially lasting beyond the end of the Devouring Plague DoT itself.

It hits hard. 99% damage may not sound like a lot on such a weak spell, but you can really feel the oomph. Running Solace and Insanity obviously increases the value of Divine Insight, but it also makes sense to use any of the other tier-6 talents with it when they're applicable.

Using Insanity

It is a damage gain (albeit a small one) to prematurely-refresh DoTs shortly before casting Devouring Plague if they would expire during the Insanity period.

Given the option, it is obviously worthwhile to begin an extra Mind Flay (Insanity) immediately before Devouring Plague would expire, allowing you to channel about 2 seconds beyond the end of the effect.

I've read that Mind Blast is higher priority than Mind Flay (Insanity), but by my math, the damage you lose by delaying Mind Blasts (and also the resultant Insanity phases) is approximately equal to the damage you gain from greater Insanity utilization right now. Even so, I believe you should use Mind Blast if it comes off cooldown; the Devouring Plague damage makes that a small damage gain.

Do not cast DoTs during Insanity, and use tier-7 talents only if you would lose the opportunity to do so if you delayed them (for example, AoE targets no-longer clumped for Halo if you wait.)