2.4 thorns build theorycrafting

set: Thorns of the invoker
(2) Set Bonus: Your Thorns damage now hits all enemies within a 15 yard radius around you. Each time you hit an enemy with Punish, or Slash, or block an attack your Thorns damage is increased by 50% for 2 seconds.
(4) Set Bonus: You take 50% less damage for 8 seconds after casting Bombardment.
(6) Set Bonus: Attack speed of Punish, and Slash increased by 50% and deal 600% of your Thorns damage to the first enemy hit.

build 1.0: http://www.d3planner.com/171475675
build 1.1: http://www.d3planner.com/442057627
build 2.0: http://ptr.d3planner.com/795391952 updated with ptr items and heavens fury synergy.

Place holder items: Captain crimson should be 5'th and 6'th slot of invoker set.

Not shown:
Heart of Iron has new bonus. http://i.imgur.com/c8vbtAe.png (changed to 400%-500% of vitality).
Justice Lantern has new bonus. "Gain damage reduction equal to 65% of your Block chance".
Endless walk set is changed to http://i.imgur.com/5ldlogM.jpg
Plague of thorns legendary gem. http://i.imgur.com/GfU8W7B.png
"Gem - Plague of Thorns: Add Adds 30000 Thorns damage. 1500 thorns per rank. At rank 25 your Primary skills Taunt the first enemy hit or 2 seconds"
"Passive - Hold Your Ground: Block chance granted increased from 15% to 30%"
"Passive - Iron Maiden: Thorns bonus increased from 50% to 100%"
"Thorns damage granted by socketing a Marquise Topaz gem rank or higher in a weapon has been greatly increased"
"The damage range of the Thorns affix on items has been increased"

General idea:
Maximize thorns damage in any way possible. Clump monsters together so thorns apply as often as possible and survive based on insane values of defense.

strategy:
We want to be hit.
We want to survive.
We want to hit as many mobs as possible.
We want to hit as fast as possible so we can apply thorns and increase 2 set stack.
Taunts and other abilities that cause monsters to hit us are thus great.
Punish best rune is Celerity is best rune but Slash - Carve or Zeal seems to be even better. Slash will hit more monsters and will generally gain a higher 2 set stack. Even more so with Omnislash.
We have 4 cooldown based skills, so we want a high uptime for them. Especially Provoke and Iron Skin. Akarat's Awakening with max block chance is used for that.

Thorns damage:
([Total Thorns roll on gear] [20000 Thorns from Topaz] [Thorns from Legendary Gem] [Up to 6 * Vitality]) * (([Strength rolled on gear] [Strength from gems]) * (1 (0.015 * [# of Gems Equipped])))

Multipliers:
Hack: 100% of your thorns damage is applied on every attack.
2 set bonus: Each time you hit an enemy with Punish, or Slash, or block an attack your Thorns damage is increased by 50% for 2 seconds.
Iron Maiden: Thorns bonus increased by 100%.
Enemies affected by Provoke that double damage from thorns.
Reflective Skin: while active, you deal 200% thorns damage to all attackers.
Sanguine Vambraces: Chances on being hit to deal 1000% of your thorns damage to nearby enemies.
Steed Charge - Spiked Barding: Deals 500% of your Thorns damage every second as you run.
Concecration - Bed of Nails: Enemies in the area of the Consecration also take damage equal to 100% of your Thorns every second.
Bombardment - Barrels of Spikes: Each barrel also deals 1500% of your Thorns damage on impact.
Thorns damage is physical. So it is boosted by 200% from Convention of Elements.
Thorns damage seems to be increased by general damage also such as Focus & restraint. Blizzard is also actively fixing bugs around this ("Fixed an issue that prevented the 50% damage bonus from Focus from increasing Thorns damage").

In order to apply thorns more often we prioritize increase attack speed as third best stat.
Primary Stat order is: Vitality > Strength > Attack Speed > Life% > All resist > Life per Hit > Armor.
Secondary Stat: Thorns damage > rest.
It is pretty much confirmed that crit and crit dmg does not scale with thorns.

I'm not sure how Bane of Stricken interact with thorns damage but if it do, it is too good to pass up.

Defense:
We want to get to 75% block cap for akarat's awakening and 2 set bonus.
Strength add 100% to thorns damage just as normal damage is multiplied.
Vitality adds (not multiplies) 500% to thorns damage so Vitality is not only a great defense stat but also a great offense stat.

Vitality on gear, vitality gems and life% together increase hitpoint pool to ridiculous values. This is where Simplicity's strength comes in. 2% healing of maximum hitpoint pool scale very well with this setup.

Bombardment belt makes sure set bonus is always triggered for 50% damage reduction.
Justice lantern add up to 48.75% further damage reduction.
Endless Walk reduce add another 50% reduction while moving.
Iron skin add another 50% reduction.
Law of Justice add up to 60% reduction.
Unity add 50% reduction.

Ring slot in kanai's cube is optional. Other rings to conside are:
Obsidian ring of the zodiac would be optimal if resource spending was used more. Unfortunately it is not.
Oculus ring for damage.
The Ess of Jordan for more clumping up.
Convention of Elements for that sweet 200% Physical boost.

How can this build be improved? Any obvious errors?

Edit:
I rewrite and modify this build as more data come in.

Very interesting build from https://www.reddit.com/r/Diablo/comments/3sxauj/24_ptr_blessed_thorns_crusader_now_with_more/
I have clearly underestimated that Hack deals damage to any attack. So abilities that trigger multiple times per second apply insane thorns damage.