Monday, May 31, 2010

Power Word: Shield (Rank 12)

In Burning Crusade the developers did a lot of tinkering with downranking. When the expansion first came out, downranked spells were super fantastic. While spell power accounts for a lower percentage of healing than it does for damage, lowering the base effect to lower the mana cost was a trade people were all too happy to make. In fact, it hardly made any sense to cast your most powerful rank of a healing spell in any situation, since they generally cost quite a lot more and only healed for a comparatively small amount more. They put in some arcane calculations to make downranking worse by lowering the spell power coefficients of spells that were learned at levels lower than a character's current level. These occasionally even lowered the spell power of your highest rank of a spell, since sometimes the highest rank was learned more than 5 levels before you hit max level. In Wrath they decided to kill downranking once and for all by making lower ranks of spells cost the same amount as higher ranks.

Despite this, I've been casting a lot of Power Word: Shield (Rank 12) recently. With the ICC buff and a fully powered Demonic Pact I could be shielding around eleven thousand damage. Or I could cast a shield two ranks lower and shield around seven and a half thousand damage. Same cost, just a worse effect; that's what I'm doing.

Discipline priests get a lot of mana return from Rapture. Rapture gives back 2.5% of the caster's maximum mana every time one a shield breaks. It does not give back any mana if the shield expires without breaking, even if the shield only has 1 point of absorb left. This effect can only occur every 12 seconds, but if multiple shields break at precisely the same time, the 12 second cooldown is unable to trigger in time, allowing all of them to return mana. Normally you wouldn't even consider this, as 30 seconds is a long time for a shield to absorb all the damage its going to absorb. But there are a number of factors at play that make downranking the right move on Lich King.
  1. Infest does just a little less damage than is required to break a full powered shield
  2. Because of the mechanics of infest it is not acceptable to let one shield cover two consecutive casts; each infest must hit a fresh shield
  3. The lich king has no other splash or AoE damage during phase one
  4. The mana return from Rapture is necessary to keep up with the healing demands of the fight
Heroic 10-player Lich King does 11.7k to 13.2k damage with Infest. This is reduced by resistances, which average 20%, and reduced by Renewed Hope, making the average hit 9680. If I cast a fully powered Power Word: Shield then the shield would hold against this damage. The only way the infest breaks the shield is if it rolls near max damage (13,218) and the victim gets only a 10% resist (about a 25% chance). This will happen sometimes, but much less than most of the time.

Infest from heroic Lich King is a serious problem that the healers don't have a lot of leeway to deal with. Allowing the debuff to be applied to more than one or two non-tanks probably means it will be fatal, which means a wipe. If someone takes 9680 through a 7300 point shield then they end up taking 2380 damage. As this is less than 10% of their maximum health, they infest debuff will fall off immediately. If the same person gets an 11k shield then the first infest reduces that to a 1320 shield. That means the next infest will do over 8000 damage to them on average, and they will need heals to clear the debuff unless their total health is over 80k. Because your buffer to avoid the Infest debuff is your shield + 10% of your health, the two smaller shield approach generally allows the target to take more than 10.5k and still not get the debuff. The single large shield approach, however, doesn't get to use the 10% health buff from the first infest. In order to succeed at preventing the infest debuff from two consecutive infests it would need to be enormous, in excess of 16k shielded. This won't be reached even with a 30% ICC zone buff and level 277 gear.

Therefore a shield is needed for each non-tank for every infest. In addition to that, there is no real difference between someone coming out of an infest with 90% health and someone coming out with 100% health. Judgement of Light or other splashing heals will heal them to full before the next infest. Given that, the larger shield doesn't actually protect any better than the smaller one.

Finally, the mana cost of healing lich king is extreme. Infest happens every 23-25 seconds, usually closer to 23. With eight shields per infest, that means spending over 230 mana a second on shields alone. Since nearly every GCD is spent on one of Renew, Penance or Flash Heal, mana spent per second on this fight is probably around 500 for priests. Discounting Rapture, 2500 mp5 is not an attainable goal. If my shields never break to infest, that is what would be needed to keep up with the healing. With shields breaking on every infest, that's over 800 mana times 8 shields every 23 seconds. By downranking, Rapture is providing about 1400 mp5. It is also providing 2% mana every 23 seconds to other casters in the raid (about 40% of a replenish) and rage, runic power and energy to the non-mana users in non-trivial amounts.

Rapture has has this problem for a long time, but for a long time there was no circumstance where it could rightly be called a problem. The developers did this because they were solving another problem: they didn't want discipline priests to simply cast shields for mana regen when they were running around. Rapture is only supposed to give you mana back if you are actually using the shield to prevent damage, not if you are casting it just for fun. I can understand that goal. They didn't think much of the problem that having shields that were too large could prevent you from getting your mana back. After all, what were the odds that discipline priests were going to start complaining that their shields were too large?

It took a very strange confluence of events to make discipline priests worry about their shields being too large. But it just happened to happen on the encounter that is the culmination of the entire expansion. It also happened to happen on an encounter where discipline priests are favoured (some would say required) for healing. While resto druids are complaining that they don't have the tools to heal infest, discipline priests are busy intentionally reducing their best spell by a third of its power to properly deal with infest.

Is all of this a mere quibble? What difference does it really make if I downrank on one fight because of a bizarre mechanic?

The problem it causes is that it makes how powerful I am seem irrelevant. If I had more spell power I would just have to drop another rank of Power Word: Shield, and having the wrong amount of spell power might be a disaster. More crit wouldn't be benefiting that task at all. I spend nearly the entire fight under the effects of Borrowed Time so my haste hits a soft cap around 154 rating and does very little after that point. With the massive mana regen from Rapture and Infest I have no use for additional Int.

I've also considered redoing my spec to get rid of Improved Power Word: Shield. But what would I take in it's place? The lich king has no effects that are affected by Unbreakable Will. Reducing my threat with Silent Resolve would similarly have no effect. Should I put two points in absolution to save myself 250-300 mana over the course of the entire fight?

There may be a non-facetious argument in favour of switching my gems to stamina, a bizarre situation to say the least.

My gear doesn't feel like it's making me better, my talent points are wasted in talents that aren't helping just because the alternatives don't help either, and I am intentionally throwing away a third of the effect of my most powerful and often cast spell. Time to go take on the hardest boss in the world!

1 comment:

  1. Your gear will make you better in Ruby Sanctum, if that is any consolation.