I don't know if this issue is known to Bungie, but kills with Ball lightning (Chaos reach melee) doesn't proc Crown of Tempest perk (speeding up arc ability regeneration). And its been that for quite a long time.
Please up vote this post for getting their attention
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This is listed in the [url=https://www.bungie.net/en/Forums/Post/251164099?sort=0&page=0]Season of the Drifter Known Issues article[/url]. [quote]Warlock Ball Lightning Melee: We are investigating an issue where the Ball Lightning melee isn't activating the Trench Barrel perk nor the Crown of Tempests' Conduction Tines perk.[/quote]