According to Araxis, a rogue guildmate:
It seemed like this had a snowball's chance in hell of being true, but this is Blizzard we're talking about, so you never know. It would be a significant find if it were true in that raid groups would want to make sure to cast Divine Spirit warriors and rogues in addition to their mana-using members. It would also fit into the rogue mythos that Blizzard hates rogues, because you know, being able to ambush people for 2.5k non-crit just isn't enough. Araxis and I set out to test this theory thoroughly.
Supposedly, there's a theory going around in rogue forums that spirit reduces chance to crit. His claim:
200 swings on a priest friend fully geared showed a lot less crits than same priest friend who is naked. Being that the only thing that should affect crit is defense, it seems rather implausible. However, Caydiem has said on forums before "What if Spirit can reduce the chance to crit?"
200 swings seem awfully low though. So perhaps I will let it run for 1000 swings. Seems like an interesting change if not reported.
We first tested Araxis's crit rate while I (as a priest) wore no spirit gear, so I had the base priest spirit of 130. In addition, I checked to make sure I didn't have any +dodge% or +agility items on. Araxis then attacked me from behind using only auto-attack. The tooltip indicated he should have a crit rate of 27.9%, and his weapon gives +3 dagger skill.
We then tested Araxis's crit rate after I put on spirit gear, which mostly consisted of Transcendence items. In addition, Jivox, a fellow priest, cast Divine Spirit on me and I used a Spirit of Zanza potion for an additional +50 spirit buff. (I also used a Gizzard Gum, but it turned out that it doesn't stack with the Spirit of Zanza). This gave me a total of 361 spirit. I again checked to make sure I didn't have any +dodge% or +agility items on, and I didn't wield a weapon just in case wielding one would create any wierdnesses with an unlisted parry or something.
Araxis used Damage Meter to tabulate the hits and crits during the tests, and we tested each case for 2,000 hits.
When I had 130 spirit, Araxis reported crit rate of 32.5% after 2,000 hits. After only 1,000 hits, he had a crit rate of just over 32.0%, so the crit rate seemed to hover around this 32-33%ish range pretty consistently.
When I had 361 spirit, Araxis had a reported crit rate of 33.8% after 2,000 hits. At first, this may sound like a grand discovery that wearing spirit actually causes the crit rate against you to go up (Omg! Priests are screaming everywhere!), but this is likely due to some slightly skewed data. The test started off with an abnormally high crit rate. For the first 400-500 hits, Araxis's crit rate was on the order of 38%. For a while, we thought we might be on to some grand discovery. (Maybe spirit does affect crit rates but Blizzard got the sign wrong in the formula?). But as more data came in, the numbers began to normalize. By 1,098 hits, Araxis's reported crit rate was down to 34.5%, and it settled down to 33.8% by the end of the test. I suspect that if we continued for 10,000 hits, the crit rate probably would have settled in the 33%ish range.
Conclusions and Discussion
A target's spirit value does not affect one's crit rate to any visible degree. Too bad. No great discovery here.
The difference in the crit rate between that reported by Damage Meter (33%ish) and that reported by the tooltip (27.9%) can be explained by how the two perform their calculations. The tooltip crit rate is one's overall crit rate per swing (hits and misses) whereas Damage Meter reports crit rates only on hits. Araxis's miss rate was 13%, and dividing 27.9% by .87 gives a hit-only crit rate of 32%, which is approximately what we found. Thanks to Concillian at the Lurker Lounge along with information gleaned from the Elitist Jerks forum for this information.