Since I like the skill and somes tooltips are missing I tried to list what could impact it in order to maximize its damage. Most of thoses have been tested, other are deduced from the game mechanics.
Main take away from it :
attack speed scale everything, as stated in the skill description.
so does strength and attunement (untested for the combined skills)
the three elements include a physical part, wich put elementals modifiers at 2/3 efficiency (1/2 for somes combined, stronger, spell) . That's a big downside of the skill
2 spells are dot, and the others can hit and apply ailments (and proc equipments/shaman lightning). Since the two dot have a cold component, frosbite can be a interesting way to scale damages with tempest strike
Please make your own testing and confirm and infirm this if you are interested, I'll update