I DID NOT WRITE THIS: VUX of Dragonblight did. I'm just reposting here as its pretty good information and kinda wasted on the WoW forums where i found it.
I decided to do some extremely in-depth testing of all the talents and spells on the PTR to see how they interacted with each other. There is quite a lot going on, especially since talents affect various spells and whether everything was additive, multiplicative, before spellpower, after spellpower, etc was a huge question.
All questions I decided to find out the answers to.
I started with a 0/0/0 spec and tested every single dot one by one. After seeing how each particular spell behaved, I added talents, one by one, continuing down the Affliction tree.
Here are my results:
(Summary of results can be found at the bottom of Post #2. Check out the Everlasting Affliction math at the beginning of Post #2 though, not only because it's a new talent, but because it's a very very awesome talent once you really understand how it works.
Affliction Tree Stress Testing
* Test I: 0/0/0 spec
o Curse of Agony
+ 0 Spellpower
56, 56, 57, 57, 113, 113, 113, 113, 170, 169, 169, 170 = 1356 total damage (Base Damage)
+ 1376 Spellpower
194, 194, 194, 194, 251, 251, 251, 251, 307, 307, 307, 307 = 3008 total damage
+ Theoretical Formula to Match Results
1356 + 1376*1.20 = 3007.2
+ Conclusion(s):
Curse of Agony has a 120% Spellpower coefficient.
o Corruption
+ 0 Spellpower
150, 150, 150, 150, 150, 150 = 900 total damage (Base Damage)
+ 1376 Spellpower
356, 356, 356, 356, 356, 356 = 2190 total damage
+ Theoretical Formula to Match Results
900 + 1376*.9375 = 2190
+ Conclusion(s):
Corruption has a 93.75% Spellpower coefficient.
* Test II: Improved Curse of Agony 2/2 (+10%)
o Curse of Agony
+ Base Damage:
1356 total damage
+ 1376 Spellpower
213, 214, 213, 214, 275, 275, 276, 276, 338, 338, 338, 338 = 3308 total damage
+ Theoretical Formula to Match Results
(1356 + 1376*1.20) * 1.1 = 3307.92
+ Conclusion(s):
Improved Curse of Agony acts after Spellpower.
* Test III: Improved Corruption 5/5 (+20%)
(Edit: Oct 21, 2008: This talent has since been changed to 10%, but I am leaving the math at 20%, so as to keep the numbers consistent with the tests that follow.)
o Corruption
+ Base Damage:
900 total damage
+ 1376 Spellpower
437, 438, 437, 437, 438, 438 = 2625 total damage
+ Theoretical Formula to Match Results
(900 + 1376*.9375) * 1.2 = 2628
+ Conclusion(s):
Improved Corruption acts after Spellpower.
* Test IV: Empowered Corruption 3/3 (+36% Spellpower)
o Corruption
+ Base Damage:
900 total damage
+ 1376 Spellpower
536, 537, 537, 537, 537, 537 = 3221 total damage
+ Theoretical Formula to Match Results
(900 + 1376*(.9375 + .36)) * 1.2 = 3222.432
(900 + 1376*(1.2975)) * 1.2 = 3222.432
+ Conclusion(s):
Empowered Corruption yields a total Spellpower coefficient of 129.75%.
* Test V: Siphon Life 1/1
o Siphon Life
+ 0 Spellpower
63, 63, 63, 63, 63, 63, 63, 63, 63, 63 = 630 total damage (Base Damage)
+ 1376 Spellpower
200, 200, 200, 201, 201, 201, 201, 201, 201, 201 = 2007 total damage
+ Theoretical Formula to Match Results
630 + 1376*1.00 = 2006
+ Conclusion(s):
Siphon Life has a 100% Spellpower coefficient.
* Test VI: Shadow Mastery 5/5 (+10%)
o Corruption
+ Base Damage:
900 total damage
+ 1376 Spellpower
581, 581, 581, 581, 581, 582 = 3487 total damage
+ Theoretical Formula to Match Results
(900 + 1376*1.2975) * 1.3 = 3490.968
+ Conclusion(s):
Improved Corruption and Shadow Mastery are addtive. (20% + 10%)
Improved Corruption and Shadow Mastery both act after spellpower.
o Curse of Agony
+ Base Damage:
1356 total damage
+ 1376 Spellpower
233, 233, 233, 233, 300, 300, 301, 301, 368, 368, 369, 369 = 3608 total damage
+ Theoretical Formula to Match Results
(1356 + 1376*1.20) * 1.2 = 3608.64
+ Conclusion(s):
Improved Curse of Agony and Shadow Mastery are addtive. (10% + 10%)
Improved Curse of Agony and Shadow Mastery both act after spellpower.
o Siphon Life
+ Base Damage:
630 total damage
+ 1376 Spellpower
220, 220, 220, 221, 221, 221, 221, 221, 221, 221 = 2207 total damage
+ Theoretical Formula to Match Results
(630 + 1376*1.00) * 1.1 = 2206.6
+ Conclusion(s):
Shadow Mastery acts after spellpower.
o Curse of Doom
+ Base Damage:
4200 total damage
+ 1376 Spellpower
6952, 6952, 6952
+ Theoretical Formula to Match Results
(4200 + 1376*2.00) * 1.00 = 6952
+ Conclusion(s):
Curse of Doom has a 200% Spellpower coefficient.
Shadow Mastery has no effect on Curse of Doom. (BUGGED)
* Test VII: Contagion 5/5 (+5%)
o Corruption
+ Base Damage:
900 total damage
+ 1376 Spellpower
603, 604, 604, 604, 604, 604 = 3623 total damage
+ Theoretical Formula to Match Results
(900 + 1376*1.2975) * 1.35 = 3625.236
+ Conclusion(s):
Improved Corruption, Shadow Mastery, and Contagion are addtive. (20% + 10% + 5%)
Improved Corruption, Shadow Mastery, and Contagion all act after spellpower.
o Curse of Agony
+ Base Damage:
1356 total damage
+ 1376 Spellpower
242, 242, 243, 243, 313, 313, 314, 314, 384, 384, 384, 384 = 3760 total damage
+ Theoretical Formula to Match Results
(1356 + 1376*1.20) * 1.25 = 3759
+ Conclusion(s):
Improved Curse of Agony, Shadow Mastery, and Contagion are addtive. (10% + 10% + 5%)
Improved Curse of Agony, Shadow Mastery, and Contagion all act after spellpower.
* Test VIII: Unstable Affliction 1/1
o Unstable Affliction
+ Base Damage (From MMO/Wowhead, unable to test without Shadow Mastery):
875 total damage (Base Damage)
+ 1376 Spellpower
495, 495, 495, 495, 496 = 2476 total damage
+ Theoretical Formula to Match Results
(875 + 1376*1.00) * 1.1 = 2476.10
+ Conclusion(s):
Unstable Affliction's coefficient was nerfed from 120% to 100% due to the 18 to 15 sec length nerf.
Shadow Mastery acts after spellpower.
# Test IX: Everlasting Affliction 5/5 (+5% Spellpower per tick)
* Corruption
o Base Damage:
900 total damage
o 1376 Spellpower
697, 697, 697, 697, 697, 697 = 4182 total damage
o Theoretical Formula to Match Results
Derivation:
(900 + 1376*1.2975) * 1.35 + (1376*.05*6) * 1.35 = 4182.516 (Add EA damage)
(900 + 1376*1.2975 + 1376*.05*6) * 1.35 = 4182.516 (Bring inside parentheses)
(900 + 1376*1.2975 + 1376*.3) * 1.35 = 4182.516 (Multiply .05*6)
Final:
(900 + 1376*1.5975) * 1.35 = 4182.516 (Sum Final Coefficient)
o For further evidence, compare ticks before and after EA:
604 + 1376*.05*1.35 = 697, which matches the above ticks
o Conclusion(s):
Everlasting Affliction gives 5% Spellpower to each tick, for a total of 30% extra damage from Spellpower (6 ticks).
Everlasting Affliction occurs before Improved Corruption, Shadow Mastery, and Contagion.
Everlasting Affliction yields a total Spellpower coefficient of 159.75% for Corruption.
* Unstable Affliction
o Base Damage:
875 total damage
o 1376 Spellpower
571, 571, 571, 571, 571 = 2855 total damage
o Theoretical Formula to Match Results
Derivation:
(875 + 1376) * 1.1 + (1376*.05*5) * 1.1 = 2854.5 (Add EA damage)
(875 + 1376 + 1376*.05*5) * 1.1 = 2854.5 (Bring inside parentheses)
(875 + 1376 + 1376*.25) * 1.1 = 2854.5 (Multiply .05*5)
Final:
(875 + 1376*1.25) * 1.1 = 2854.5 (Sum Final Coefficient)
o For further evidence, compare ticks before and after EA:
495 + 1376*.05*1.1 = 571, which matches the above ticks
o Conclusion(s):
Everlasting Affliction gives 5% Spellpower to each tick, for a total of 25% extra damage from Spellpower (5 ticks).
Everlasting Affliction occurs before Shadow Mastery.
Everlasting Affliction yields a total Spellpower coefficient of 125% for Unstable Affliction.
* Siphon Life
o Base Damage:
630 total damage
o 1376 Spellpower
296, 296, 296, 296, 296, 296, 296, 296, 297, 297 = 2962 total damage
o Theoretical Formula to Match Results
Derivation:
(630 + 1376) * 1.1 + (1376*.05*10) * 1.1 = 2963.4 (Add EA damage)
(630 + 1376 + 1376*.05*10) * 1.1 = 2963.4 (Bring inside parentheses)
(630 + 1376 + 1376*.50) * 1.1 = 2963.4 (Multiply .05*10)
Final:
(630 + 1376*1.50) * 1.1 = 2963.4 (Sum Final Coefficient)
o For further evidence, compare ticks before and after EA:
220 + 1376*.05*1.1 = 296, which matches the above ticks
o Conclusion(s):
Everlasting Affliction gives 5% Spellpower to each tick, for a total of 50% extra damage from Spellpower (10 ticks).
Everlasting Affliction occurs before Shadow Mastery.
Everlasting Affliction yields a total Spellpower coefficient of 150% for Siphon Life.
# Test X: Haunt
* Haunt
o Base Damage (From MMO/Wowhead, unable to test without Shadow Mastery):
487-569 base (528 avg) (Base Damage)
o 1376 Spellpower
Hits: 1158, 1173, 1184, 1158, 1225, 1213, 1233, 1227, 1218, 1216, 1191, 1194, 1243, 1200, 1156
Crits: 1734, 1754, 1792, 1777, 1821
Total Average: 1195.3833
o Theoretical Formula to Match Results
Derivation:
(528 + 1376*x) * 1.1 = 1195
x = 40.568%
This is very close to the coefficient for any instant cast spell (1.5/3.5 = 42.857%)
Final:
(528 + 1376*.42857) * 1.1 = 1229 (close to my average, even though I had a very small sample size)
o Conclusion(s):
Haunt has a 42.857% Spellpower coefficient.
Haunt crits were nerfed to do 150% damage (before build 8970, they did 200% damage).
# Test XI: Dot Ticks with Haunt + 2 Stacks of Shadow Embrace
(Some of these ticks are higher due to 5% increased zone damage from PVP objectives. Didn't realize it until after a few tests.)
* Corruption
o Tick Before Haunt + Shadow Bolt: 731
o Tick After Haunt + Shadow Bolt: 967
o 967 / 731 = 1.3228
* Curse of Agony
o Tick Before Haunt + Shadow Bolt: 254
o Tick After Haunt + Shadow Bolt: 337
o 337 / 254 = 1.32677
* Siphon Life
o Tick Before Haunt + Shadow Bolt: 311
o Tick After Haunt + Shadow Bolt: 410
o 410 / 311 = 1.318
* Unstable Affliction
o Tick Before Haunt + Shadow Bolt: 599
o Tick After Haunt + Shadow Bolt: 792
o 792 / 599 = 1.3222
* Conclusion(s)
o 100% Damage + 20% Haunt + 10% SE = 1.30 multiplier (does not match results above)
o 100% Damage * 1.2 Haunt * 1.1 SE = 1.32 multiplier (matches results for all dots)
o In other words, Haunt and Shadow Embrace both act multiplicatively and on top of all talents and spellpower.
o Haunt and Shadow Embrace DO increase dot damage if dot is casted first, and then Haunt/SE after.
# Overall Test Conclusions
* Talent modifiers are always additive. The lump sum of talent modifiers is then is multiplied after spellpower.
* Any buffs (on yourself) and any debuffs (on the target) are multiplicative.
# Bugs
* Death's Embrace is currently bugged to do nothing. Will update this once it is fixed.
* Curse of Doom is bugged. It does not get any benefit from Shadow Mastery, even though it does shadow damage.
# Summary of Results
* Corruption: (900 + Spellpower*1.5975) * 1.35
* Curse of Agony: (1356 + Spellpower*1.20) * 1.25
* Siphon Life: (630 + Spellpower*1.50) * 1.1
* Unstable Affliction: (875 + Spellpower*1.25) * 1.1
* Curse of Doom (Bugged): 4200 + Spellpower*2.00
* Haunt + 2 Stacks of Shadow Embrace: Tick * 1.20 * 1.10