I re-forged Gheleon's Demise many times and finally got one I liked. It has the "lightweight" upgrade in which you gain +2 agility when holding the weapon. The perk simply isn't taking affect. I have the MIDA Multi-Tool and the perk works just fine.
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It's not really that noticeable Plus the Mida has the perk that increases your movement speed, which I what I believe you're noticing the Gheleon doesn't have.