Thread summaries:

Oglas has written a summary of research so far at post #500 (page 20). Please note, not everything listed there has been throughly tested, but it's the best we've got so far.

My brief summary:

Weapon skill acts differently, depending on whether the skill difference is >10 or <= 10.

Weapon Skill does not seem to affect parry, block or glancing rates. Weapon skill does affect dodge rates. See post #32 for data.

The base miss rate against Level 73 bosses is 9.0% (28% for dual wielding). This is higher than previously expected. See post #383 for test details.


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Original post:

This has been somewhat discussed in the Rogue Damage Spreadsheet thread, but after reading through pages 41-60 of that thread, I still wasn't sure if a conclusive testing result was reached.

So in brief...

Old Conventional Wisdom stated that Weapon Skill was the opposite of defense skill. As such, it conferred a 0.04% gain to your hit/crit chances and a -0.04% to your opponent's dodge/parry/block chances. The old view is well summarized on WoW Wiki's Weapon Skill Page.
Additionally, there was a blue patch note that Weapon Skill also increased your Crit RATING (not crit value) by a small 0.1% per skill point if you were fighting monsters above your level.

The new theory is based on an post on the EU Forums in response to the general complaint that Weapon Skill was useless (which it nearly is under the Old Conventional Wisdom). This post claims that against a mob 3 levels higher than you, each point of weapon skill provides 0.2% to your hit/crit chance, and -0.6% parry, -0.1% dodge to your opponent.

This discussion is about whether the old model, the new model, or some other model is correct.

The new model has one major thing going for it: The new numbers make weapon skill useful. Blizzard has historically stated that Weapon Skill is the best use of an itemization point, however under the old math this statement was not true, in fact, it wasn't even close to true.
On the minus side, the new model seems to provide very strange numbers for the actual effect. Why -0.6% parry, but only -0.1% dodge? Also, by having weapon skill NOT the opposite of defense skill, you end up with strange behavior when one side has improved weapon skill and the other side has improved defense skill.

Of course, who needs speculation when people can TEST! Based on posts in the Rogue Damage Spreadsheet thread, it seems like there is some backing for weapon skill providing 0.1% increase to hit, but only 0.04% increase in crit. Does the new model cause weapon skill to have any effect on your opponent's dodge/parry/block rates?

I did some testing posted in the rogue thread versus some lower level mobs. At 45 skill more I did experience parries and dodges but at 50 skill plus I didn't notice anything for some 3000 swings. This data set could be larger I know but it got pretty boring :P

If it's 0.1% per skill point that is what would be expected I guess.

This also makes weapon skill a great tanking stat since we're the only ones hitting stuff in the face. Mallet of the tides and that black temple axe...

But it would be nice with a really huge parse from a beefed up +skiller and someone without versus only bosses. Wiping at Onyxia maybe?

This is for dual wielders i assume? Does anyone have some info on if it works differently for a feral druid?

This definitely applies to Druids too. The major difference is that we tank with a 2-hander like that pug warrior you had for your last ZF group

Earthwarden
Binds when picked up
UniqueTwo-Hand Mace
142 - 279 Damage Speed 3.20
(65.8 damage per second)
500 Armor
+39 Stamina
Durability 120 / 120
Requires Level 70
Requires Cenarion Expedition - Exalted
Equip: Increases defense rating by 27.
Equip: Increases feral combat skill rating by 24.
Equip: Increases attack power by 556 in Cat, Bear, Dire Bear, and Moonkin forms only.

Good stuff.

So I did some testing on dodge/parry. I went to Zangamarsh and ran autoattacks on the Bogflare Needlers (guaranteed level 62) for about 15 minutes. I am a 11/43/7 Mace specced rogue. Unfortunately that means that the Needlers spent a lot of time stunned, and when they weren't stunned they were sometimes casting (which I believe prevents them from dodging/parrying).

360 Weapon Skill, 187 Hit Rating, +5% Precision
1580 Total Attacks
1533 Landed (97.03%)
31 Missed (1.96%)
15 Parried (0.95%)
1 Dodged (0.06%)

The 1 dodge was pretty disheartening, since I got it near the end. =) Apparently, it means that Weapon Skill does not quite provide -0.1% to your opponent's dodge per level, but it's definitely far more than the old -0.04%. The real number of attacks I had where the needler wasn't casting or stunned is probably closer to 800, so I would consider the real parry rate to be about 2%.

Or maybe those extra skill you have above your level (WEx) only applies to mobs (defense) above your level. That is after all what the blue post stated about crit. I did my testing without the WEx talent.

Good point. I'll try running a test with daggers (I only have the +10 to maces). On the other hand, there was a pretty significant discrepancy between dodge and parry, so that bit of info is interesting.

If theoretical value is 1%, then anything between .5% and 1.5% is within statistical bounds for 1500 swings. 2% is actually pretty unlikely.

The test was originally to check to see if Weapon Skill was causing -0.1% dodge/parry rate per level. I had 360 weapon skill during the test against level 62 mobs (310 defense). I got a whole bunch of parries, and a single dodge. So, the theory of -0.1% per point of weapon skill against lower level opponents isn't the right one unless bonus skill (Weapon Expertise) is counted differently than innate skill.

The percentages from this test are NOT really worth very much because:
A) I am mace specced, which means that even with just autoattacks, the guys ended up stunned for long periods
B) Needlers have a spell they cast periodically. When players are casting, they can't dodge, block, or parry. I'm unsure if this is also true for mobs, but assuming it is, then I got free hits in during this time.

I'll try this conceptual test again with 350 weapon skill against level 60s to try to verify Punscho's data.

It most likely is not true, I have had shield bashes parried and dodged when a mob is casting (I'm fairly certain they have been blocked before too, but the spell is still interrupted so I don't usually go back and look at my combat log). I might be incorrect in assuming special attacks are treated the same as white damage however.

Pummel has a lower damage range than shield bash though (doesn't it?) if it's fully blocked, then the pummel won't go through, whereas a shield bash would be partially blocked, but the interrupt would still go through. I'm pretty sure this works the same as with kick for rogues.