I summoned a Lightbringer that was 2 levels too low also.  However, the Summon Ignys was the correct level so maybe that's a clue.  Are the Life Shard level-ups not being applied (or maybe they're not supposed to be applied in which case you need to update the text).

I saw this, it seemed to me that the life shard bonuses were not applying - my summons were too low by exactly my life shard count.

Simply put the code isn't add the lifeshard in it

        <GameModifier>
            <ModType>Unit</ModType>
            <Attribute>SummonUnit</Attribute>
            <UnitClass>Wisp</UnitClass>
            <ApplyToSpellRadiusCenterOnly>1</ApplyToSpellRadiusCenterOnly>
            <Duration>-1</Duration>
            <Calculate InternalName="Calc" ValueOwner="CastingUnit">
                <Expression><![CDATA[[UnitStat_BonusSummonLevel] + 2]]></Expression>
            </Calculate>
            <Calculate InternalName="Value">
                <Expression><![CDATA[[Calc]]]></Expression>
            </Calculate>
        </GameModifier>

It really should read.

     <GameModifier>
            <ModType>Unit</ModType>
            <Attribute>SummonUnit</Attribute>
            <UnitClass>Wisp</UnitClass>
            <ApplyToSpellRadiusCenterOnly>1</ApplyToSpellRadiusCenterOnly>
            <Duration>-1</Duration>
            <Calculate InternalName="Calc" ValueOwner="CastingUnit">
                <Expression><![CDATA[[UnitStat_BonusSummonLevel] + [UnitOwner_GetNumLifeShards]]]></Expression>
            </Calculate>
            <Calculate InternalName="Value">
                <Expression><![CDATA[[Calc] + 2]]></Expression>
            </Calculate>
     </GameModifier>

A similar fix for the tactical version of the spell.

Here is a fix for the problem, just drop this spell into your mods folder (or items folder so you don't need to run mods) and poof it will work as the description says it should. The fix includes lightbringer as well.

https://dl.dropboxusercontent.com/u/75549875/Fallen%20Enchantress/Abilities/SummonWispSummonLightBringerFix.zip

I agree, that is why I provided the feedback to find exactly the bug to the spell, I showed exactly what is needed to be fixed for the spell, and I provided them with a template that they can use to update the spell if they choose to use it. I'm just providing the feedback that I would expect when someone asks me a question.