Tanking: Discussing the Effect of Expertise for Reducing Incoming Damage

Hey guys, was having a look around regarding this, seeing as ToC gears is riddled with expertise I wanted to look deeper into the stat,
And its benefit to a tank beyond the boss' dodge cap,

I would have put this in the Paladin section of the forum, but as its applicable to all tanks, and is more relevent to warriors then paladins, i thought i'd start a thread here to discuss how you guys feel about it.

Anyways, looking around the net i found a very interesting article here (have a read if you like maths): http://maintankadin.failsafedesign.com/forum/index.php?f=6&t=25611&start=0&rb_v=viewtopic

Its findings suggest that expertise is 0.73% as effective as dodge, for reducing incoming dmg.

Basically, the benefit of expertise in terms of damage reduction revolves around the parry-haste mechanic, which as we know, once a boss parrys an attack from a tank, he benefits from a 40% reduction in the time remaining till his next swing. So the more the boss parrys a tank the more the tank gets hit over the duration of the fight.

So how much does the boss parry, and how much extra incoming damage can we avoid by reducing those parrys?

How much does a boss parry?.. well its generally though of as about 10% parry rate, but in fact it could be much higher depending on the boss. I tested this on the lv83 training dummy, of 30mins of auto-attacking. The results were, given that i have 37expertise (9.25%) 1100 auto atacks resulted in 50 parrys on my melee swing (4.5%) and an additional 59 parrys of my holy vengeance. That puts the heroic training dummy on about a 13.75% parry rate. So if a raid boss has a similar parry rate to the dummy, your talking about 109parrys during a 30min test, ok lets average that down to a 10minute fight, the boss would get the benefit of 36 parry-hasted swings from paladins auto-attack.

Thats bad for a prot paladin, but for a warrior the situation is worse, given that they put our far more parryable attacks, and dont benefit from the Glyph of SoV, a warrior on 5% expertise would give the boss nearly twice the number of parry-hasted attacks from his auto-attack compared to a paladin with similar gear, and even more addtional parry-hasted attacks, since he has more parryable abilities. Since an Ulduar/ToC geared tank is prolly sitting on 55% avoidance, the chances of you taking a hit + a parry-hasted hit straight after is fairly remote in most fights, but over the course of a fight like algalon, you are going to be hasting a great number of attacks and taking a significant amount of addtional damage through the parry-haste mechnanic.

So should we probably be looking at trying to reach near the parry cap in terms of gear, with an expertise figure in the 50s moving into IC? i know effective health is still the king, so i wouldnt ever say gem for expertise, but should we be trying to pick up more?

I know the maths works out, i took a good hour pouring through the figures myself (that the sort of thing i do at work that makes me look busy :p).. but ill certainly be looking at expertise as a defensive stat, as well as a threat stat.

Any thoughts?

In most fights where parry-haste can cause potential tank deaths, the boss is flagged as not hasted by parry, we've seen this on gormock in toc, thorim in ulduar, and even brutallus and illidan back in tbc.
Its a strong argument, but when it comes to it, blizz dosnt like parrys killing tanks

yeah.. ur right.. the ones i know that arent parry-hasted are patchy, ignis.. didnt know about gorm,
But its not that it will kill a tank nowadays, is was a bigger problem cause of crushing blows in TBC.. that could batter a tank down if you got unlucky series of parry-hasted attacks,

I think its more useful now as just, not only avoiding a few extra blows over time, but more smoothing out potential dmg spikes, and saving healers work/mana through that.. if the dmg is going on the tanks smoother they can time their big heals/abilities better.. useful for longer mana-critical and or healing intensive fights,

After all thats what we aim for by trying to build huge health pools.. giving healers breathing room to cast big efficient heals, I think anything we tanks can do to smooth out incoming damage.. the better. :-)

Thing is i was reading some of the stuff on IC, and basically starting out when patch 3.3 is released, they are saying that bosses will be able to 2 or 3 shot a tank, so some unlucky RNG could result in HIT + PARRYHASTED-HIT.. when the tank isnt fully topped up, and that could mean tank death and a wipe. Its not so much a problem for prot paladins.. AD FTW but for other classes it could be.