A Magicka Templar DPS (damage dealer) build using the Back-Alley Gourmand set in place of the crafted Order's Wrath for extra crit. Make sure you have a food buff running for the new set's 5-piece bonus. Ghastly Eye Bowl is a good choice.

Switch to back bars and use Radiant Oppression for execute after boss reaches 42% health.

As long as you are confident in maintaining uptime on Degeneration, you can even use regular Essence of Magicka potions instead of expensive Essence of Spell Power (or Spell Critical, which is provided by the slotted Mage's Guild Inner Light ability).

Use Barbed Trap sparingly if you are often low on stamina. It is a potent DoT, but you still get get the Fighter's Guild "Slayer" passive for it even if you don't have the stam at the moment.

Like other Update 35 & 36 off-meta builds that eschew two-handed weapons in favor of staff on the back bar and are more fun/easier to play, the back-bar slot 2 & 3 abilities are flex slots. If you need a shield or other help depending on content or group, these are the places for them.

It almost goes without saying, but even if you think you have months of meta stability, only gold out the jewelry if you actually have the mats to spare. It's usually prohibitively expensive, and players almost always regret it.