That is because the spell itself needs to have the multiplication of -1 as below. For some reason it has yet to get that fix from the last time.

<SpellDef InternalName="Bleed_Ability">
        <DisplayName>Bleed</DisplayName>
        <Description>Attack that does normal damage and 3 damage per action to the victim.</Description>
        <FormattedDescription>Attack that does normal damage and %d damage per action to the victim.</FormattedDescription>
        <IconFG>Ability_Bleed_Icon.png</IconFG>
        <Cooldown>5</Cooldown>
        <SpellBookSortCategory>Unit</SpellBookSortCategory>
        <SpellBookSortSubCategory>Other</SpellBookSortSubCategory>
        <SpellType>Tactical</SpellType>
        <SpellClass>Offensive</SpellClass>
        <SpellSubClass>Debuff</SpellSubClass>
        <SpellTargetType>EnemyUnit</SpellTargetType>
        <HideInHiergamenon>1</HideInHiergamenon>
        <IsCastable>0</IsCastable>
        <CanBeDodged>1</CanBeDodged>
        <IsSpecialAbility>1</IsSpecialAbility>
        <UseWeaponRange>1</UseWeaponRange>
        <GameModifier>
            <ModType>Unit</ModType>
            <Attribute>DefendableDamage</Attribute>
        </GameModifier>
        <GameModifier>
            <ModType>Unit</ModType>
            <Attribute>CurHealth</Attribute>
            <IsForFormattedDescription>1</IsForFormattedDescription>
            <Duration>-1</Duration>
            <Effect>Bloody_OnHit</Effect>
            <PerTurn>1</PerTurn> 
             <Calculate InternalName="Calc" ValueOwner="CastingUnit">
                <Expression><![CDATA[3 + [UnitStat_BonusBleed]]]></Expression>
            </Calculate>
            <Calculate InternalName="Value">
                <Expression><![CDATA[[Calc] * -1]]></Expression>
            </Calculate>
            <Calculate InternalName="ValueForFormattedDescription">
                <Expression><![CDATA[[Calc]]]></Expression>
            </Calculate>
        </GameModifier>
        <AIData AIPersonality="AI_General">
            <AIPriority>5</AIPriority>
        </AIData>
        <HitSoundFX>Spell_Knockback_01</HitSoundFX>
        <SpellDefEffect>
            <EffectName>Ability_ShieldBash_Particle</EffectName>
            <LocalPosition>0,0,0</LocalPosition>
            <EffectScale>0.25</EffectScale>
            <EffectDelay>0</EffectDelay>
            <SnapToTerrain>1</SnapToTerrain>
        </SpellDefEffect>
    </SpellDef>

CoreSpells.xml

You could just copy what I wrote above, and put it in its own separate xml file and put it in the mods folder (run mods and the fix will be present)

Parrot, do you have a "Donate Paypal" account or something? I swear you fix more errors than Stardock and I have always donated to modders once I settle into a game anyway.

I updated the file as you suggested, but bleed still gives healing instead of damage.

C:\Program Files\Steam\steamapps\common\FE Legendary Heroes\data\English\CoreSpells.xml

When does the CoreSpells.xml get read? During each battle or is it assigned to the hero on the upgrade? What I have done to test the change is to replay a battle from a save file; it seems the save file is now updating or reading the CoreSpells.xml. Could that be?