He spreads Rupture more efficiently to the Ursoc Images, which you did poorly
That not only ensures a better EP uptime on his side, but also provides more energy to dump on Envenoms ( which he managed to do almost the same amount as you, and still more efficient than you, checking the "avg. cast" on Envenom )
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Also, you not only have to maintain Rupture on the images, but poisons on them as well, so they can actually return energy to you