I've been looking for proper source to pile together all current PvP spell multipliers which has proven way more difficult than I was expecting. While there are several blogposts and reblogs most fail to mention if previous multipliers are still in effect and only list changes. Many changes are also only ever mentioned on twitter.
Having hidden effects (like mage poly glyph being build in to spell itself) doesn't really help this.
Is there any comprehensive list of multipliers anywhere?
Amusingly blizzard official thread which they tell us to check for current info seems to be dead end with 404: http://us.battle.net/forums/en/wow/topic/20747314610
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Edit: alright, I'm changing my approach.
Here is my current list to best of my knowledge. If you find something incorrect or missing please point me in right direction.
MAGE
ArcaneRune of Power increases damage by 35% in PvP (instead of 50%)
Frost Rune of Power increases damage by 35% in PvP (instead of 50%)
Glacial Spike deals 100% damage in PvP (was reduced to 75% but has since been un-nerfed)
FireRune of Power increases damage by 35% in PvP (instead of 50%)
Cauterizing Blink heals for 50% in PvP
Fireball deals 250% damage in PvP
Pyroblast deals 70% damage in PvP
PALADIN
HolyAll damage done reduced by 25%
Holy Shock deals 50% damage in PvP
ProtectionAll damage done reduced by 15% in PvP
All damage taken increased by 25% PvP
Avengers Shield deals 50% damage in PvP
Shield of the Righteous deals 50% damage in PvP
Light of the Protector heals for 85% in PvP
Hand of the Protector heals for 85% in PvP
Retribution
Execution Sentence deals 85% damage in PvP --(Update)
Templars Verdict deals 70% damage in PvP --(Update, upped 100% as in multiplier removed)
Justicars Vengeance deals 60% damage in PvP --(Update, upped 100% as in multiplier removed)
Justicars Vengeance heals for 60% of damage done --(Update, upped 100% as in multiplier removed, looking for source)
Justicar's Vengeance deals 50% additional damage to stunned targets in PvP (down from 100%) --(Update)
DRUID
Balance No Multipliers (does Fullmoon have multiplier? I though it had but haven't been able to find source on this)
FeralAshamane's Frenzy deals 50% damage in PvP
Guardian All damage done reduced by 15% in PvP
All damage taken increased by 25% PvP
Rage of the Sleeper deals 50% damage in PvP
RestorationAll damage done reduced by 25%
Livebloom’s bloom effect increased by 50% in PvP
HUNTER
BeastmasteryMurder of Crows deals 65% damage in PvP
Barrage deals 80% damage in PvP
Cobra Shot deals 75% damage in PvP
Kill Command deals 80% damage in PvP
MarksmanshipMurder of Crows deals 65% damage in PvP
Aimed Shot deals 80% damage in PvP
Marked Shot deals 50% damage in PvP
Piercing Shot deals 50% damage in PvP
Exhiliration heals for 60% in PvP
Healing Shell effects reduced by 50% in PvP
SurvivalMurder of Crows deals 65% damage in PvP
Barrage deals 80% damage in PvP
Mongoose Fury increases the damage of Mongoose Bite by 35% per stack in PvP
PRIEST
Discipline All damage done reduced by 15%
Atonement healing is increased by 15% in PvP
HolyAll damage done reduced by 25%
Shadowno PvP multipliers (to my knowledge)
MONK
BrewmasterAll damage done reduced by 15% in PvP
All damage taken increased by 25% PvP
Mistweawer All damage done reduced by 25%
Revival heals for 200% in PvP
Soothing Mist healing reduced by 10% in PvP
Soothing Mist healing (Jade Serpent Statue) reduced by 10% in PvP
WindwalkerFists of Fury deals 70% damage in PvP
Strike of the Windlord deals 70% damage in PvP
ROGUE
AssassinationCrimson Vial heals for 50% in PvP
Death from Above increases the effect of Envenom, Run Through and Eviscerate by 25% in PvP (down from 50%)
Nightstalker increases ability damage by 25% in PvP
Rupture deals 75% damage in PvP
Blood of the Assassinated increases rupture damage by 30% in PvP
OutlawCrimson Vial heals for 50% in PvP
Death from Above increases the effect of Envenom, Run Through and Eviscerate by 25% in PvP (down from 50%)
Nightstalker increases ability damage by 25% in PvP
Between the Eyes’s damage bonus on Critical Strikes reduced to 100% in PvP
SubtletyCrimson Vial heals for 50% in PvP
Soothing Darkness heals for 50% in PvP --(Update)
Death from Above increases the effect of Envenom, Run Through and Eviscerate by 25% in PvP (down from 50%)
Nightstalker increases ability damage by 25% in PvP
Shadowstrike deals 70% damage in PvP
Eviscerate deals 85% damage in PvP --(Update)
Nightblade deals 85% damage in PvP
Finality has 60% of its effect in PvP
SHAMAN
ElementalLava Bursts from Elemental Overload deal 60% damage in PvP
Earth Shock deals 75% damage in PvP
EnhancementStormstrike’s damage is reduced by 15% in PvP
Doomwinds increases Windfury damage by 120% in PvP
Healing Surge heals for 50% in PvP
RestorationAll damage done reduced by 30%
Lava Burst deals 80% damage in PvP (Restoration only)
Healing Surge heals for 120% in PvP
Healing Wave heals for 135% in PvP
Healing Stream Totem heals for 125% in PvP
WARLOCK
AfflictionDemon Skin's passive recharge effect has 50% effect in PvP (0.5% of maximum health every second in PvP)
Absolute Corruption grants Corruption a 40 second duration in PvP
DemonologyDemon Skin's passive recharge effect has 50% effect in PvP (0.5% of maximum health every second in PvP)
Thal'kiel's Consumption deals 66% damage in PvP
DestructionDemon Skin's passive recharge effect has 50% effect in PvP (0.5% of maximum health every second in PvP)
Chaos Bolt deals 120% damage in PvP
DEATHKNIGHT
Blood All damage done reduced by 15% in PvP
All damage taken increased by 25% PvP
Unending Thirst increases damage and leech by 15% in PvP
Hearth Strike does 75% damage in PvP
Blood Boil does 30% damage in PVP
Frost Sindragosa's Fury deals 40% damage in PvP
UnholyApocalypse deals 75% damage in PvP
Dragged to Helheim deals 80% damage in PvP
Virulent Plague deals 75% damage in PvP
Dark Arbiter's Val'kyr Strike deals 70% damage in PvP
Epidemic deals 85% damage in PvP
WARRIOR
Arms Bladestorm deals 66% damage in PvP
Focused Rage increases the damage of Mortal Strike by 20% in PvP
Fury Bladestorm deals 66% damage in PvP
ProtectionAll damage done reduced by 15% in PvP
All damage taken increased by 25% PvP
Focused Rage increases the damage of Shield Slam by 20% in PvP
Ignore Pain absorb is reduced by 20% in PvP
Shield Block increases Shield Slam damage by 12% in PvP
DEMONHUNTER
HavocMetamorphosis leech reduced by 60% in PvP
Fury of the Illidari damage is now reduced by 10% in PvP
VengeanceAll damage done reduced by 15% in PvP
All damage taken increased by 25% PvP
Soul Fragments from Shattered Souls heal for 20% in PvP
Soul Barrier absorbs are 20% in PvP
My intention was to include this info in small addon I've been working on. (had hoped to include anything that can't be found in tooltips)