Thorns on The Crusader actually works really well, but there are a couple of legedaries and set items you will need to make it work.
Let me sum this up for you, here are the items that is pretty much required.
Ring of The Royal Grandeur - This will reduce the amount of items you need in a set to get the bonus by one (1).
The Invoker set - (Helm, shoulders and gloves prefferbly) This is why you need the Ring of The Royal Grandeur, the 4 set bonus from The Invoker set makes all your thorns damage to deal damage to all enemies within 15 yards.
Sanguary Vambraces - Chance on being hit to deal 1000% of your thorns damage to nearby enemies.
Hack - (One-Hand Axe) Your thorns damage is dealt with every attack.
Those are the items you pretty much require to have, there are also two shields that might be useful;
Defender of Westmarch - Blocks have a chance to summon a charging wolf that deal 300-400% damage to everyone it passes through. (This item procs ALOT and deals great damage.)
Vo'Toyias Spiker - Enemies affected by provoke takes double damage from thorns. (This shield also has alot of thorns damage on it)
I think that sums the items up pretty well.
Now for the spells, notice this is my personal opinion.
Left-Click: Punish (Retaliate) - Keep the effect from this up 100% of the times.
Right-Click: Shield Bash (Shttered Shield) - Gives mobility and deals a decent amount of damage.
Button 1: Iron Skin (Reflective Skin) - Nice 200% additional thorns damage dealt to attackers aswell as some tankyness.
Button 2: Steed Charge (Endurance) - For the mobility and speed.
Button 3: Laws of Valor (Critical) - Nice bonus attack speed for wrath generation and extra damage output.
Button 4: Provoke (Hit Me) - Nice extra 50% block chance from the rune and makes mobs hit you instead of others.
The passives are the following:
Passive 1: Iron Maiden - Nice extra thorns damage.
Passive 2: Hold Your Ground - 15% extra block chance, this is especially good with Defender of Westmarch shield, but has nice survivability bonus aswell.
Passive 3: Divine Fortress - Nice extra survivability for tanking mobs and letting them hit you.
Passive 4: Heavenly Strength - NOTICE! Only use this if you do NOT have the axe named Hack. If you do have Hack use Vigilant or Renewal instead.
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