Theorycrafting: Divine Illumination

In the comments on my Holy Paladin introduction post, where I discussed various talent specs for a holy pally, Raquel disagreed with my decision to leave Divine Illumination out of the “bare minimum” spec. Now, I’ve been thinking about picking DI back up again, so let’s take a bit of a look at it.

Divine Illumination is the end talent of the Holy tree for paladins, not to be confused with Illumination or Divine Intervention (which is the usual ability indicated by the ‘DI’ abbreviation). Divine Illumination “reduces the mana cost of all spells by 50% for 15 seconds”, and is on a 3 minute cooldown. (Note that this effect does not apply to Lay on Hands; you still drain all your mana when you blow LoH regardless of this spell.)

Now, the actual mana savings of Divine Illumination are really dependent on your own casting rotation, and the situations under which you’re healing. Obviously, you’re going to get a lot more use out of it in fights where you’re frantically chain-casting your biggest heals just to keep the tank up than you are when you’re leisurely throwing Flash of Lights in a controlled environment.

That said, let’s do a bit of hypothetical numbercrunching. I’ll use my own spell rotation for this, which tends to be approximately three Flash of Lights and then a Holy Light – on average, that is; obviously it’s situational, but over the course of most (progression and newly-on-farm) fights I throw about 25% Holy Lights, 75% Flash of Lights.

Now, again, assume a chain-casting situation, which means that during the 15 seconds Divine Illumination is up, I’m going to wind up throwing 2 Holy Lights and about 6 Flash of Lights – theoretically 7 Flash of Lights, but there’s always a bit of latency (especially for us Aussie players), having to move around, whatever.

So, 2x Holy Lights = 1680 mana and 6x Flash of Lights = 1080 mana, for a total of 2760 mana used in that fifteen seconds. A 50% savings is 1380 mana – in other words, Divine Illumination saves me 1380 mana every 3 minutes, or 460 mana per minute (on average). That’s an equivalent of 38.3 mp5, which is pretty huge for one talent point.

Obviously, that’s not the same as mp5; it’s a mana savings, not a mana return, which means that – just like mana return on crit heals – if you’re not casting, you’re not getting the benefit of this talent. And, like other cooldowns, if you don’t use it, you don’t get the benefit, either. Use it every time it’s up, unless it’s a spiky-damage fight where you know you’ll be throwing out a string of big heals before the cooldown will be up again.

That said, for progression fights where you’re chain-casting or close to it, Divine Illumination certainly looks like it’s worth the talent point – provided you remember to use it.

2 thoughts on “Theorycrafting: Divine Illumination”

  1. I smirked at “provided you remember to use it.” as I constantly forgot to use it in a lot of fights I wasn’t solo-healing someone in a corner.

    PS – I think this was the first time I’ve been mentioned in a non-RL friend blog’s post. :)

  2. Fame at last! :D

    I’ve actually macro’d DI in with my Holy Light spell, so it gets tripped any time I cast HL. That may not be /the/ most efficient way of doing it, but at least it means it gets used. (I do the same thing with my clicky trinkets on Flash of Light.)

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