Per disease on a target this spell should do 12.5% more weapon damage…

…. At the moment it do the 12.5% extra damage from the spells damage which only hits for 25% weapon damage. So the extra damage is only 3.125% of weapon damage. For this the damage mod should be 50% cause 50% of 25% is 12.5%.

src/server/game/Spells/SpellEffects.cpp

@@ -3428,7 +3428,7 @@ void Spell::EffectWeaponDmg(SpellEffIndex effIndex)
             // Blood-Caked Strike - Blood-Caked Blade
             if (m_spellInfo->SpellIconID == 1736)
             {
-                AddPctF(totalDamagePercentMod, unitTarget->GetDiseasesByCaster(m_caster->GetGUID()) * 12.5f);
+                AddPctF(totalDamagePercentMod, unitTarget->GetDiseasesByCaster(m_caster->GetGUID()) * 50.0f);
                 break;
             }
             // Heart Strike