I noticed a debuff on the Bears doing the maul attacks. Sure enough, there's XML linked up to the maul debuff.
It begins in the ElementalDefs.xml:
<MaulDebuffSpell>MaulDebuff</MaulDebuffSpell>
and in CoreSpells.xml you will find
<SpellDef InternalName="MaulDebuff">
<DisplayName>Maul Debuff</DisplayName>
<Description>Effect after a successful Maul attack</Description>
<IconFG>Ability_Maul_Icon.png</IconFG>
<IconColor>210,110,210</IconColor>
<SpellType>Tactical</SpellType>
<SpellClass>Defensive</SpellClass>
<SpellSubClass>Debuff</SpellSubClass>
<SpellTargetType>Self</SpellTargetType>
<HideInHiergamenon>1</HideInHiergamenon>
<IsCastable>0</IsCastable>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Accuracy</StrVal>
<Duration>1</Duration>
<Value>-4</Value>
</GameModifier>
<AIData AIPersonality="AI_General">
<AIPriority>5</AIPriority>
</AIData>
</SpellDef>
The debuff is lacking <CanStack>0</CanStack> which means it does stack.
To test if it was working properly, I put this in instead
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Accuracy</StrVal>
<Duration>1</Duration>
<Multiplier>0</Multiplier>
</GameModifier>
and gave a unit 200 accuracy and maul. Result: Maul was triggered from first hit, second hit always misses at 0 Accuracy.
This one would decrease Accuracy and Physical damage by 25% of original value for every hit performed while in Maul-mode.
<SpellDef InternalName="MaulDebuff">
<DisplayName>Maul Debuff</DisplayName>
<Description>Effect after a successful Maul attack</Description>
<IconFG>Ability_Maul_Icon.png</IconFG>
<IconColor>210,110,210</IconColor>
<SpellType>Tactical</SpellType>
<SpellClass>Defensive</SpellClass>
<SpellSubClass>Debuff</SpellSubClass>
<SpellTargetType>Self</SpellTargetType>
<HideInHiergamenon>1</HideInHiergamenon>
<IsCastable>0</IsCastable>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Accuracy</StrVal>
<Duration>1</Duration>
<Multiplier>0.75</Multiplier>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Attack_Blunt</StrVal>
<Duration>1</Duration>
<Multiplier>0.75</Multiplier>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Attack_Pierce</StrVal>
<Duration>1</Duration>
<Multiplier>0.75</Multiplier>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Attack_Cutting</StrVal>
<Duration>1</Duration>
<Multiplier>0.75</Multiplier>
</GameModifier>
<AIData AIPersonality="AI_General">
<AIPriority>5</AIPriority>
</AIData>
</SpellDef>
Since the value is given immediately after the first hit, the maximum amount of damage a unit with this could deal is 1+0.75+0.5+0.25=2.5.
Let me just remind everyone, since this is somewhat of a hot topic, that reporting feedback on a modded game is very, very stupid, and your feedback will have no value, in fact it will make the devs' job harder.