Screenshots of my Bloodthirsty Spearmen (+25% attack vs damaged enemies) in melee range of two enemies, one injured and one not.

As you can see by the tool tip in the second image, they are apparently receiving no bonus against the damaged enemy.

Here are the GameModifiers from CoreAbilities.xml

<GameModifier>
                <ModType>Unit</ModType>
                <Attribute>AdjustUnitStat</Attribute>
                <StrVal>UnitStat_Attack_Blunt</StrVal>
                <Multiplier>1.25</Multiplier>
                <Provides>+25% Blunt Attack vs Damaged Opponents</Provides>
                <vsDamaged>1</vsDamaged>
            </GameModifier>
            <GameModifier>
                <ModType>Unit</ModType>
                <Attribute>AdjustUnitStat</Attribute>
                <StrVal>UnitStat_Attack_Cutting</StrVal>
                <Multiplier>1.25</Multiplier>
                <Provides>+25% Cutting Attack vs Damaged Opponents</Provides>
                <vsDamaged>1</vsDamaged>
            </GameModifier>
            <GameModifier>
                <ModType>Unit</ModType>
                <Attribute>AdjustUnitStat</Attribute>
                <StrVal>UnitStat_Attack_Pierce</StrVal>
                <Multiplier>1.25</Multiplier>
                <Provides>+25% Piercing Attack vs Damaged Opponents</Provides>
                <vsDamaged>1</vsDamaged>
            </GameModifier>

I see no value tag and it makes me wonder if the Multiplier tag is working properly.