Shaman · Enhancement · tier 4 · from level 25

Stormstrike

+58.9 Earth Shock

1/1 · level 60 · per cast · on targets hit by your Stormstrike · and 2 more

Stormstrike

Rank 1/1

Instantly strike for normal weapon damage and increase the damage you deal to the target with your next Lightning Bolt, Chain Lightning, or Earth Shock spell by 20% for 12 sec.

Earth Shock +58.9 Lightning Bolt +39.3 Chain Lightning +24.7

Averages, counting crits and misses, for a level 60 Shaman with a typical weapon and no other gear or buffs, against a target your level. Worked out from the game's own data, the same way as the Foresight addon.