Sunder Burner™ Reverse Knockback Sunder Elementalist with Emberwake Ignite Prolif

After playing a vanilla, Physical Damage based Sunder Marauder, I was very pleased with the skill's mechanics and AoE capabilities, however, I found it severely lacking in terms of single target DPS. Sunder is inherently very safe for a single target ability due to its range, and I really wanted to come up with a way to make it viable as such.

I came to the conclusion that the most effective way of increasing single target DPS would be by scaling a source of auxilliary damage via proliferating a DoT effect from the blue packs near map bosses. This could be achieved by Poison, with Bino's in offhand or by Ignites, with Emberwake and Elemental Proliferation/Beacon of Ruin. I put together skill trees for each and concluded that it was more efficient to scale Fire Damage instead of Poison, while still getting as much AoE and Life as possible. The easiest way to get consistent Ignites was by choosing the Elementalist Ascendancy for Elemental Conflux, and Proliferation via Beacon of Ruin.

Now I had to solve the riddle of scaling the Hit and Burn Damage most efficiently; this is achieved by maximizing instances of double dipping. These include increases Fire Damage, Elemental Damage, Area Damage, and (Universal) Damage. Since I would be scaling Fire Damage, I decided to use flat Fire Damage as a base. Immediately, Dyadus came to mind as it has top tier Fire DPS for a 1h Axe/Mace. This in turn led to the notion of using Dyadian Dawn as well for 20% more* Burning Damage and 0.6% Life Leech against Chilled enemies.

One problem with Burning Damage is that it is affected twice by enemy resistances; once for the hit, and again for the Ignite. The best way to overcome this was to stack this double dipping in our favour. I decided to run both Elemental Weakness and Flammability on Blasphemy. With our Curse Effectiveness from the tree and 20% quality Blasphemy we can attain 40% increased Curse Effectiveness. Therefore, with level 20 Flammability and Elemental Weakness we have a total of ((44%+39%)*1.4) 116% reduced enemy Fire Resistance or 123% with 20/20 Elemental Weakness.

Main Hand
The best option is Dyadus. When buying one, prioritize the Attack Speed roll over the Fire Damage since you can get added Fire Damage but not base attack time elsewhere.

Off Hand
3G Prismatic Eclipse 36% increased Global Attack Speed and 10% more Attack Speed from Dual Wielding so damn sexy. It is a HUGE increase to your DPS and movement speed via Whirling Blades. 8% increased Block Chance while Dual Wielding is nice too.
Advancing Fortress
This weapon provides a middle ground between Dual Wielding and 1h/shield. 15% increased Block Chance, decent Life and ES make it quite defensive while keeping the 10% more Attack Speed from Dual Wielding. With fortify already linked, yoy can like Whirling Blades to Reduced Mana or some other utility support. It is probably the best option for HC.
Rare Shield
Only consider using a rare shield if you haven't capped your resists. The other options are superior, especially in terms of clear speed.

Chest
Carcass Jack
This is the only real option for us. We need the Life, Resists, AoE, and ES since we are running EB. I wouldn't settle for anything else, even in HC.
Belt
Dyadian Dawn
Great Life, Resists, Damage, and Leech. The Strength is nice as well but corrupted with +1 Endurance Charge would be ideal.

Rings & Amulet
Emberwake
Mandatory, gotta stack those burns baby.
Doedre's Damning
+1 Curse is mandatory so this is the only option until you can get a corrupted amulet. Remember, all you need on the Amulet is 15% or more Total Elemental Resistance to make it superior to Doedre's
Rare Ring/Amulet
Go for Life and Resistances primarily. After that, get some Accuracy, flat Fire Damage, and/or Dexterity if you can.
The Taming
If you can get your hands on this your DPS will be ludicrous. Capping Resistances will be harder but well worth it.

Boots
Lioneye's Paws
These are an extremely efficient and affordable choice. They give amazing Dexterity and Strength as well as flat Fire Damage which you can't otherwise get on boots.
Rare Boots
Depending on how you achieve your Stat and Resistance requirements, these might be your best option.

Gloves
Empire's Grasp
We only use these for the reverse Knockback, get them as soon as you can.
Rare Gloves
Only use if you are struggling to cap your Resistances or Stats.

Helm
Rare Helm
This is one of your key pieces of gear for Life and Resistances. Getting some ES is nice as well be mindful of the colour of the links you want to roll.

Flasks
Seething Seething Life Flask
For those OH SHIT moments.
Rumi's Concoction
Unrivaled defensive bonuses; 38% Block Chance from a perfectly rolled one after the increases to Flask Effect.
Lion's Roar
This is our source of Knockback, the more Physical Damage does benefit us a bit from Dyadus' flat Phys and Avatar of Fire.
Basalt Flask of Iron Skin
So much Physical mitigation... How did this Flask make it into the game? Inb4 Nerfbat.
Silver Flask
Onslaught is too good to pass up; it will increase your clear speed more than Sulfur Flask. Try to get a good utility roll such as of Heat, of Warding, or of Staunching.

Jewels
Priorities (in order):
ES on hit (6+ to feel comfortable)
Life
Resistances
Fire Damage
Area Damage
Damage
Attack Speed
Damage over Time

No Regen
Just don't use Blood Rage and you'll be fine.

Blood Magic / Curse Immune
These two are essentially impossible for us.

Elemental Reflect
This mod might be possible by swapping WED for Life Leech and using a Sybil's Lament. Have not yet tested.