Pob: https://pastebin.com/bQUk0wPk

This is the general premise of the build: with a very high speed we cast Crackling Lance, the cost of which we make sure to be over a 100 mana. So, with every cast we have a 50% chance to trigger the spells in our helmet, Storm Call and Hydrosphere. To buff their damage we cast a very juicy Arcane Cloak. The idea is that we still have very good clear while at high Intensity.

Two notable things about our ascendancies: Elementalist makes Hydrosphere's Exposure very strong. Raider, while giving us insane cast speed, also gives perma Phasing. This allows us to make excellent use of Mistwall. Although, if defence is not an issue, dual wielding is probably best.