The version of Stormstrike in Season of Discovery does not trigger Maelstrom Weapon, and does not trigger many other chance on hit abilities/weapon skill increases.
Stormstrike damage in Vanilla/Classic is displayed as white damage, but in SoD it is displayed as yellow damage despite the tool-tip still saying ‘Gives you an extra attack’.
I have not seen any notes from Blizzard’s end on this matter, so until then it is a bug.