With the latest Patch the PvP gear was finally added to the game. Due to this the relevance of PvP and the PvP Stats increased as more people are doing battlefields now! For this reason I started doing research on PvP Offense and PvP Defense.
Before I start, I want to thank Bruce for helping me with this tests!

Please note: This is currently for Lv40 only, it is possible that we will have other values at Lv45/Lv50.

General Information
PvP Offense and PvP Defense do not increase/decrease the DMG in PvP by a fixed amount! They are multipliers which modify your DMG/Mitigation in a PvP based situation. Also it is very important to know that they do not work directly against each other like PvP Offense – PvP Defense = increase/decrease, I will pick up on this later once we start to talk about the calculations!

PvP Offense
100 PvP Offense = +1,4% DMG against a player
PvP Offense is multiplying your DMG against other players.

PvP Defense
100 PvP Defense = -1,4% DMG received a player
PvP Defense is decreasing your received DMG from other players.

Please note: There is a diminishing return for both, PvP Offense and PvP Defense, still this diminishing return is so small that the difference at 3600 is lower than 3% and I am not talking about the a 3% difference in DMG.

3600 PvP Defense = 49,1% Mitigation – DR added
3600 PvP Defense = 50,4% Mitigation – no DR

=2,56% difference in the Mitigation

100% = 7350 PvP Defense – DR added
100% = 7200 PvP Defense – no DR

Highest PvP Offense / PvP Defense @Lv40
PvP Offense = 4622 > 63,4% DR / 64,7% nDR
PvP Defense = 4914 > 67,4% DR / 68,8% nDR

Calculations
The general DMG formula for Lv40 is:
DMG = DMG * (1 – (Defense / 12000))

If we know add PvP Offense / Defense:
DMG = (DMG*(1+(0,00014*PvP Offense)))*(1–(Defense/12000))*(1–(0,00014*PvP Defense))

If you remember I said that PvP Offense and PvP Defense are not working directly against each other and this formula shows why. In case PvP Defense would work directly against PvP Offense the DMG would change. Let me give you some short examples:
100 DMG / 1000 PvP Offense / 1000 PvP Defense / 0 Defense
DMG = 100 * (1 – (0 / 12000)) * (1 – (0,014 *(1000 – 1000))
DMG = 100 * 1 * 1
DMG = 100

DMG = 100*(1+0,14) * (1 – (0 / 12000)) * (1-0,14)
DMG = 100 * 1,14 * 1 * 0,86
DMG = 98

Because of this PvP Defense will always reduce the DMG received regardless of the enemies PvP Offense but this PvP Offense will always increase your DMG in PvP regardless of the PvP Defense of you target.
However in the end this makes PvP Defense superior compared to PvP Offense. While PvP Offense is multiplying your DMG before the reduction the DMG increase is higher but as PvP Defense is the final multiplier on the DMG it reduces the DMG in total and not just the increase from the PvP Offense.

Examples of PvP Defense
If you have zero Defense you will reduce your DMG by 0% – leaving 100% DMG
Adding 50% Mitigation through PvP Defense will reduce your received DMG by another 50%
100% * 50% = 50% DMG left

If you have 4000 Defense you will reduce your DMG by 33% – leaving 67% DMG
Adding 50% Mitigation through PvP Defense will reduce your received DMG by another 33%
67% * 50% = 33% DMG left

If you have 6000 Defense you will reduce your DMG by 50% – leaving 50% DMG
Adding 50% Mitigation through PvP Defense will reduce your received DMG by another 25%
50% * 50% = 25% DMG left

If you have 10000 Defense you will reduce your DMG by 83% – leaving 17% DMG
Adding 50% Mitigation through PvP Defense will reduce your received DMG by another 8,5%
17% * 50% = 8,5% DMG left

Examples of PvP Offense
100 DMG vs. 0 Defense = 100 DMG
100 DMG vs. 4000 Defense = 67 DMG
100 DMG vs. 6000 Defense = 50 DMG
100 DMG vs. 10000 Defense = 17 DMG

+50% PvP Offense

150 DMG vs. 0 Defense = 150 DMG
150 DMG vs. 4000 Defense = 101 DMG
150 DMG vs. 6000 Defense = 75 DMG
150 DMG vs. 10000 Defense = 26 DMG

PvP Offense vs All Attack
Please note: It is confirmed that points in All Attack for the Warrior / Force Shielder adding bonus DMG based on the Base DMG of their Skills. It is confirmed that Priests do not have this bonus DMG. As I am not done with the testing on the FA, FB and Wi there are three possible assumptions:
1. Assumption
FS and Wa receiving this bonus because they are melee classes. This would mean that this bonus applies to the FB as well. While FA and Wi do not get any bonus as well.

2. Assumption
FS and Wa receiving this bonus because they are Physical DMG dealers and due to the facts that most people have more Physical Defense because of PvE and there are only two full Physical DMG dealers this is a balance issue. This would mean this bonus could apply to the FBs physical DMG part as well. While FA and Wi do not get any bonus as well.

3. Assumption
Someone got bored while creating the Scalings for the Skills and started typing in random multipliers. This would mean that FA, FB and Wi might have a completely different bonus DMG from points in All Attack.

With this said I’d like to compare All Attack vs. PvP Offense for the FS and the Priest without going to deep in any calculations so you can understand the thought process in choosing either PvP Offense or All Attack in your Stat Growth.

Priest DMG
While the DMG you deal is based the base DMG and the Scaling of a Skill PvP Offense is increasing both the base DMG and the Scaling DMG while All Attack is only increasing the Scaling DMG of a Skill. The big question here is how much Attack is worth the DMG increase of PvP Offense.
While 3 Points in PvP Offense (90) increasing the DMG by 1,26% putting those points into All Attack would increase the Magical Attack by 6.

Cleasing Touch has a Scaling of 36% with a base DMG of 60.

So adding 6 Attack would increase the DMG by ~2
While just on the base DMG 1,26% would add +1 DMG

BUT we have to add the full Scaling from all Magical Attack for PvP Offense – so assuming a low Attack of only 500 > 180 DMG from Scaling + 60 from base DMG > 240 DMG

1,26% of 240 = +3 DMG

With other words the higher the base Attack from your gear the stronger PvP Offense will be but if you have low base stats PvP Offense is worse than putting points directly in All Attack.
Also – the higher the Scaling the stronger is Attack!
You cannot just decide based on the DMG of one of your skills. Choosing PvP Offense or All Attack has to be chosen with a look on all of your skills as a Skill with a low scaling might deal more DMG through PvP Offense while another Skill with a high scaling might deal less DMG because you have chosen PvP Offense.

Force Shielder DMG
The situation for the FS is somewhat different as the points you put in All Attack increase your base DMG and the DMG from the Scaling.

1 point in All Attack increases the base DMG of FS Skills by 1% in addition you gain 2 points of physical Attack which is also increasing your DMG based on the scalings.
Rend IV
DMG = 80 + (80*(1+pts in All Attack/100))+40% Physical Attack

Resulting in +5 DMG for 3 points in All Attack
While 3 points in PvP Offense would increase the total DMG by 1,26%

800 Physical Attack + 120 points in All Attack
DMG = 496

794 Physical Attack + 117 points in All Attack + 90 PvP Offense
DMG = 491 DMG + 1,26%
DMG = 497 DMG

While this small change is increasing the DMG by +1

680 Physical Attack + 60 points in All Attack + 1800 PvP Offense
DMG = 400 DMG + 25,2%
DMG = 501 DMG

This huge change is just +5 DMG however loosing 120 Physical Attack for just a +5 DMG increase might not be worth it due to the fact that you have to fight PvE Mobs in the battlefields as the DMG against them is dropping by a huge amount.
Yet again this is based on your total Attack. The higher your Attack and thus the DMG you gain from the scaling of the skill the more effective PvP Offense becomes.

But remember PvP Offense is only helping you against players directly – PvP Offense does not help you on conquering objectives or jungling on Forgotten Temple.