Its time to create fun builds again

Burning spell weave is optimal, but I don't want to.

Burning Spellweave

(2 items) Adds 1096 Maximum Magicka
(3 items) Adds 129 Weapon and Spell Damage
(4 items) Adds 657 Critical Chance
(5 items) When you deal damage with a Flame Damage ability, you apply the Burning status effect to the enemy and increase your Weapon and Spell Damage by 490 for 8 seconds. These effects can occur once every 12 seconds.

I like the idea of using an ascetically pleasing proc sets on rotation which will make me look really cool when I blood mist. 

ESO resource shows this build at 6263 penetration. If I go with the Lover Mundus, I can hit 10754 penetration. 

Crit damage starts at 50%. This build provides 75% average critical damage, with the maximum critical damage being 3% higher. If I go with fighting finesse, critical damage goes to 83%. If I decide to go with the Shadow Mundus with the CP change, then the average critical damage is at 101%. 

Usually will never use Flawless Dawnbreaker unless you are about to die. Its main purpose is to proxy for the Slayer Fighter Guild passive so that Whirlblades and Swaming Scion damage more. That's literally the whole point of this. Why magicka though? Velthoi has made it possible to spam abilities with no light attacks in between. Finally, Crystal Fragments can be used to cast with less janky-ness now…thank the gods! Of course, it doesn't hurt to hit an enemy with a light attack from our inferno staff to trigger Unfathomable Darkness, but we only have 12 seconds (+3 seconds before we can rotate to back bar) so we must be ready to rotate to the front bar for Deadric Curse>Crystal Fragments (red if we are lucky)>Whirlblade to clean up.

Other back bar sets to consider using:

Crusader

(2 items) Adds 129 Weapon and Spell Damage
(3 items) Adds 129 Weapon and Spell Damage
(4 items) Adds 129 Weapon and Spell Damage
(5 items) When you deal direct damage with a Blink, Charge, Leap, Teleport, or Pull ability, you consecrate the ground beneath you for 10 seconds and gain a damage shield that absorbs 1595 damage for 6 seconds. Every 2 seconds you and nearby group members in the area gain Minor Courage for 12 seconds. These effects can occur once every 20 seconds and the damage shield scales off the higher of your Weapon or Spell Damage.

Crimson Twilight

(2 items) Adds 1206 Maximum Health
(3 items) Adds 4% Healing Taken
(4 items) Adds 1206 Maximum Health
(5 items) After taking damage you surround yourself in an 8 meter mist of blood. After 2 seconds, the mist is violently siphoned into your body, dealing 1946 Bleed Damage to nearby enemies and healing you for 100% of the damage done. This effect can occur once every 8 seconds and scales off your Max Health.

Flame Blossom

(2 items) Adds 1096 Maximum Magicka
(3 items) Adds 129 Weapon and Spell Damage
(4 items) Adds 1487 Offensive Penetration
(5 items) When you deal damage, you summon a line of flame that moves forward after 1 second, dealing 1537 Flame Damage to any enemy in its path and applying the Burning status effect. This effect can occur once every 10 seconds and scales off the higher of your Weapon or Spell Damage.

Plague Slinger

(2 items) Adds 129 Weapon and Spell Damage
(3 items) Adds 1206 Maximum Health
(4 items) Adds 129 Weapon and Spell Damage
(5 items) When you take damage, summon a Skeever corpse which will launch five poison balls over 5 seconds that each deal 737 Poison Damage to the nearest enemy within 10 meters. This effect can occur once every 8 seconds and scales off the higher of your Weapon or Spell Damage.

Unleashed Terror

(2 items) Adds 129 Weapon and Spell Damage
(3 items) Adds 1096 Maximum Stamina
(4 items) Adds 1096 Maximum Stamina
(5 items) When you deal direct damage with a Blink, Charge, Leap, Teleport, or Pull ability, you cut your enemy, causing them to bleed for 10 seconds, dealing 1995 Bleed Damage over the duration and applying the Hemorrhaging status effect every tick. This ability can occur once every 10 seconds per target and scales off the higher of your Weapon or Spell Damage.

Rush of Agony

(2 items) Adds 129 Stamina Recovery
(3 items) Adds 129 Weapon and Spell Damage
(4 items) Adds 1487 Offensive Penetration
(5 items) When you deal direct damage with a Blink, Charge, Leap, Teleport, or Pull ability, pull enemies within 10 meters to you. After 2 seconds, deal 1705 Physical Damage to all enemies within 7 meters. This effect can occur once every 8 seconds and scales off the higher of your Weapon or Spell Damage. The pull will not apply Crowd Control Immunity to a target.

Personally, I'm leaning towards Unleashed Terror, as it works so well with blood mist and we can effortlessly trigger it every rotation for Whirlblade. Rush of Agony would be a fun dream, but we must wait 2 seconds for the physical damage to occur before switching bars. In theory, the rotation for this build would go as the following:

Hurricane>Critical Surge>Blood Mist>Wall of Elements>Swarming Scion>switch bars>Whirlblades.

It can feel weird and clunky in this specific rotation. 

So usually with the perfect conditions met, your tank is using Void Bash so your can freely Blood Mist in the trash pre-buffed and with Wall of Elements cast. Then you can freely clean up the trash and be extremely fast.