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It's still relevant because elements basically add on more (elemental damage?) to your weapon.
example:
1000 atk weapon, 50 light ---> 1000 atk, 500 light atk
1000 atk weapon, 20 light ---> 1000...

My thoughts are you only need the potential at lvl 3. No idea if the above post about it being 8mil was with/without the pot, but I'm guessing that with potential its much higher than 8mil.

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