[2.1] Blast Avatar, Crit Pure Fire Blast Rain, VP version, 22K x4hits, Ref-Proof

Test Run - The Dried Lake(That's my templar)
lv76 Crematorium, 18% Elemental Reflection
lv80 Courtyard
lv81 Shrine

5L with Kaom's Heart
BR(lv17), Fire Penetration(lv8/q20), WED(lv16/q19), Concentrated Effect(lv19/q20), FA(lv16/q20)

Offence

Defence

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6L, with 'Added Fire Damage' support.
(I don't have a 6L bow, capture this with my 6L chest, it should be more with Kaom's Heart.)

1. Convert 50% physical damage to fire damage by Avatar of Fire. With another 50% damage conversion from the skill itself, Blast Rain now do pure fire damage.

About Damage conversion see here

2. Use Lioneye's Fall to transform staff melee skill node to bow's.


3. Instant leech with Vaal Pact.

Leech life and mana from attack damage (new skill cluster at Duelist section).

Stack life for survivability.
Keystone Unwavering Stance and Iron Reflexes are options.


4. 'Pyre' is an option, you can play this build without it, but it's strongly recommended

It converts all cold damage to fire damage which makes 'Hatred' more effective. It also increase burning damage.
And the last affix works just like 'Shatter'. It grants the ability that destroy ignited enemies, thus prevents some on-death effects by monsters that could cause further damage.
About 'Freeze and Shatter' see here.

Pros:
-Rapid clear speed with 'Increased Area of Effect', great DPS with 'Concentrated Effect' for boss fight.
-Reflection proof, With 'life leech' support gem and Warlord's Mark(Purity of Fire if 'Monsters are Immune to Curses'), can do maps with Reflect 18% elemental damage.

Cons:
-Poor Jewel sockets in skill tree.
-Die easily if can't find something to leech. xD

lv92_with Unwavering Stance and Iron Reflexes
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lv70_Avatar of Fire
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lv50, 64points
Bandits:
Normal help Oak/ Cruel kill all(or help Oak)/ Merciless kill all.
You can start with Shadow/ Ranger /Duelist. Take life/ physical dmg/ bow/ crit as you level up.
Reach 'Avatar of Fire around' lv70.

Fire damage and 500 life! love it.

Before you get a nice bow like mine(xD 100% self loot and crafted. just can't get it 6L yet.) There are options that offers fair DPS. For example:

Tool tip DPS when you use 'Chin Sol' may seems a bit low, but if you fire Blast Rain around your character you'll find it does a great job. (take down Voll merciless Dried lake in 6 seconds, I guess it's not that bad.)

This is the 6L before I get a 6L bow.


If you want to focus on AOE coverage and dps Carcass Jack might be an option for you.

5L/6L Blast Rain

Gem order by priority, about Penetration see here
Remove 'Added Fire Damage' if 5L.
Replace 'Added Fire Damage'(WED if 5L) with 'Life Leech' for maps with elemental reflection.

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Actually PPAD offers a little bit more damage than Added Fire Damage or Faster Attack.
I choose Added Fire Damage instead of PPAD because of easy swapping 'Life leech' support for dealing with Reflection.
Faster Attack simply gives more APS.
Therefore we could have more critical strike per second.
Therefore more chance to gain Endurance Charge from critical strikes.
Therefore more chance to have Immortal Call last a longer time.
Therefore more chance to survive. xD

For faster clear speed, replace 'Concentrated Effect' with 'Increased Area of Effect'

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4L #1 CWDT set.

This set separate you and melee attackers also block projectiles from ranged monsters after you take damage and trigger 'Frost Wall'.
'Immortal Call' gives over 0.6s physical invulnerability with 'Increased Duration', it'll last longer if we have 'Endurance Charge'(which we get often from critical strike. xD), it's a very effective defense method.
When it comes to party, 'Frost Wall' is annoying. Here's some option:

For maps that Monsters have Critical chance/multipiler
Dealing with reflection / extra leech
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4L #2 Aura/Buff/Vaal skill

Extra cold damage from 'Hatred' will be converted to fire damage by 'Pyre'.
Besides extra fire damage, HoA ignites 130%+ overkill dmg to nearby enemies, you'll find out monsters out of BR AoE could just burned down by HoA.

On-demand option

Try get a RBGW 4L for this set, easy swap purity of elements(fire/ice/lightning) means better adaptability.
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4L #3 Movement and buff.

Vaal Haste with increased duration boost DPS and movement speed to a higher level for 10 seconds.