Chance of % Damage

Question: Tempest or Stormcaller pact for instance has this chance to proc % lightning damage.How does this stat proc? Is it based on just weapon damage skills like savagery or does it also include skills like stun jacks with no WD.

Thanks for replying

It works just as %damage would work - so it affects all spells.

It’s just less consistent.

thank you good sir