Core/Auras:

Make Aura::ModStackAmount(1) an equivalent of reapplying the aura
    Recalculate periodic aura timers on aura reapply.

src/server/game/Entities/Unit/Unit.cpp

@@ -3158,9 +3158,6 @@ Aura* Unit::_TryStackingOrRefreshingExistingAura(SpellEntry const* newAura, uint
                 *oldGUID = castItemGUID;
             }
 
-            // refresh charges
-            foundAura->SetCharges(foundAura->CalcMaxCharges(caster));
-
             // try to increase stack amount
             foundAura->ModStackAmount(1);
             return foundAura;

src/server/game/Spells/Auras/SpellAuraEffects.cpp

@@ -377,7 +377,7 @@ m_baseAmount(baseAmount ? *baseAmount : m_spellProto->EffectBasePoints[m_effInde
 m_canBeRecalculated(true), m_spellmod(NULL), m_isPeriodic(false),
 m_periodicTimer(0), m_tickNumber(0)
 {
-    CalculatePeriodic(caster, true);
+    CalculatePeriodic(caster, true, false);
 
     m_amount = CalculateAmount(caster);
 
@@ -766,7 +766,7 @@ int32 AuraEffect::CalculateAmount(Unit * caster)
     return amount;
 }
 
-void AuraEffect::CalculatePeriodic(Unit * caster, bool create)
+void AuraEffect::CalculatePeriodic(Unit * caster, bool create, bool load)
 {
     m_amplitude = m_spellProto->EffectAmplitude[m_effIndex];
 
@@ -790,9 +790,7 @@ void AuraEffect::CalculatePeriodic(Unit * caster, bool create)
             break;
         case SPELL_AURA_PERIODIC_TRIGGER_SPELL:
             if (GetId() == 51912)
-            {
                 m_amplitude = 3000;
-            }
             m_isPeriodic = true;
             break;
         case SPELL_AURA_PERIODIC_TRIGGER_SPELL_WITH_VALUE:
@@ -840,19 +838,30 @@ void AuraEffect::CalculatePeriodic(Unit * caster, bool create)
         }
     }
 
-    if (create)
+    if (load) // aura loaded from db
     {
-        // Start periodic on next tick or at aura apply
+        m_tickNumber = m_amplitude ? GetBase()->GetDuration() / m_amplitude : 0;
-        if (m_amplitude && !(m_spellProto->AttributesEx5 & SPELL_ATTR5_START_PERIODIC_AT_APPLY))
+        m_periodicTimer = m_amplitude ? GetBase()->GetDuration() % m_amplitude : 0;
-            m_periodicTimer += m_amplitude;
-    }
-    else if (m_amplitude) // load aura from character_aura
-    {
-        m_tickNumber = GetBase()->GetDuration() / m_amplitude;
-        m_periodicTimer = GetBase()->GetDuration() % m_amplitude;
         if (m_spellProto->AttributesEx5 & SPELL_ATTR5_START_PERIODIC_AT_APPLY)
             ++m_tickNumber;
     }
+    else // aura just created or reapplied
+    {
+        m_tickNumber = 0;
+        // reset periodic timer on aura create or on reapply when aura isn't dot
+        // possibly we should not reset periodic timers only when aura is triggered by proc
+        // or maybe there's a spell attribute somewhere
+        bool resetPeriodicTimer = create 
+            || ((GetAuraType() != SPELL_AURA_PERIODIC_DAMAGE) && (GetAuraType() != SPELL_AURA_PERIODIC_DAMAGE_PERCENT));
+
+        if (resetPeriodicTimer)
+        {
+            m_periodicTimer = 0;
+            // Start periodic on next tick or at aura apply
+            if (m_amplitude && !(m_spellProto->AttributesEx5 & SPELL_ATTR5_START_PERIODIC_AT_APPLY))
+                m_periodicTimer += m_amplitude;
+        }
+    }
 }
 
 void AuraEffect::CalculateSpellMod()

src/server/game/Spells/Auras/SpellAuraEffects.h

@@ -42,7 +42,7 @@ class AuraEffect
         void SetPeriodicTimer(int32 periodicTimer) { m_periodicTimer = periodicTimer; }
 
         int32 CalculateAmount(Unit * caster);
-        void CalculatePeriodic(Unit * caster, bool create = false);
+        void CalculatePeriodic(Unit * caster, bool create = false, bool load = false);
         void CalculateSpellMod();
         void ChangeAmount(int32 newAmount, bool mark = true, bool onStackOrReapply = false);
         void RecalculateAmount() { if (!CanBeRecalculated()) return; ChangeAmount(CalculateAmount(GetCaster()), false); }

src/server/game/Spells/Auras/SpellAuras.cpp

@@ -726,6 +726,16 @@ void Aura::RefreshDuration()
         m_timeCla = 1 * IN_MILLISECONDS;
 }
 
+void Aura::RefreshTimers()
+{
+    m_maxDuration = CalcMaxDuration();
+    RefreshDuration();
+    Unit * caster = GetCaster();
+    for (uint8 i = 0; i < MAX_SPELL_EFFECTS; ++i)
+        if (HasEffect(i))
+            GetEffect(i)->CalculatePeriodic(caster, false, false);
+}
+
 void Aura::SetCharges(uint8 charges)
 {
     if (m_procCharges == charges)
@@ -802,7 +812,12 @@ bool Aura::ModStackAmount(int32 num, AuraRemoveMode removeMode)
     SetStackAmount(stackAmount);
 
     if (refresh)
-        RefreshDuration();
+    {
+        RefreshTimers();
+
+        // reset charges
+        SetCharges(CalcMaxCharges());
+    }
     SetNeedClientUpdateForTargets();
     return false;
 }
@@ -871,7 +886,7 @@ void Aura::SetLoadedState(int32 maxduration, int32 duration, int32 charges, uint
         {
             m_effects[i]->SetAmount(amount[i]);
             m_effects[i]->SetCanBeRecalculated(recalculateMask & (1<<i));
-            m_effects[i]->CalculatePeriodic(caster);
+            m_effects[i]->CalculatePeriodic(caster, false, true);
             m_effects[i]->CalculateSpellMod();
             m_effects[i]->RecalculateAmount(caster);
         }

src/server/game/Spells/Auras/SpellAuras.h

@@ -127,6 +127,7 @@ class Aura
         int32 GetDuration() const { return m_duration; }
         void SetDuration(int32 duration, bool withMods = false);
         void RefreshDuration();
+        void RefreshTimers();
         bool IsExpired() const { return !GetDuration();}
         bool IsPermanent() const { return GetMaxDuration() == -1; }
 

src/server/game/Spells/Spell.cpp

@@ -1427,9 +1427,8 @@ SpellMissInfo Spell::DoSpellHitOnUnit(Unit *unit, const uint32 effectMask, bool
 
         if (m_originalCaster)
         {
-            bool refresh;
             m_spellAura = Aura::TryRefreshStackOrCreate(aurSpellInfo, effectMask, unit,
-                m_originalCaster, (aurSpellInfo == m_spellInfo)? &m_spellValue->EffectBasePoints[0] : &basePoints[0], m_CastItem, 0, &refresh);
+                m_originalCaster, (aurSpellInfo == m_spellInfo)? &m_spellValue->EffectBasePoints[0] : &basePoints[0], m_CastItem);
             if (m_spellAura)
             {
                 // Set aura stack amount to desired value
@@ -1437,8 +1436,7 @@ SpellMissInfo Spell::DoSpellHitOnUnit(Unit *unit, const uint32 effectMask, bool
                     m_spellAura->SetStackAmount(m_spellValue->AuraStackAmount);
 
                 // Now Reduce spell duration using data received at spell hit
-                // if we're refreshing aura, recalculate max duration, to avoid applying mods twice
+                int32 duration = m_spellAura->GetMaxDuration();
-                int32 duration = refresh ? m_spellAura->CalcMaxDuration() : m_spellAura->GetMaxDuration();
                 int32 limitduration = GetDiminishingReturnsLimitDuration(m_diminishGroup, aurSpellInfo);
                 float diminishMod = unit->ApplyDiminishingToDuration(m_diminishGroup, duration, m_originalCaster, m_diminishLevel, limitduration);