Looks much tougher than the actual build, which does have much better locking pistols though…
FOREWORD
After I recently tried to brighten 
your day with this beauty…
…I’m gonna give it another shot with this very special but fun and challenging class combination called Defiler, as there were not a lot of Defiler builds posted recently, which is somewhat understandable unfortunately…
THE BUILD
A more damage-oriented devotion setup didn’t work for me in Crucible.
LEVELING PROCESS
I like to level with skeletons and/or BWC as it’s fast, fun, different to just melee or ranged and there are good supporting MIs.
If you are really new to the game and don’t like to figure it out on your own, maybe check out these awesome guides from @RektbyProtoss.
EQUIPMENT
I started with the Blightlord-Set which buffs Black Water Cocktail and Ravenous Earth, added Mythical Korvaak’s Brand for the ability to dual wield pistols and some welcome buffs followed by the Gargabol pistols as they give nice Vitality RR to Thermite Mine, +1 to both classes, Vitality damage to Flame Touched and some nice conversions.
Both rings give us some nice buffs and -20% more Vitality RR.
The belt and the shoulders are a bit of a tricky one. While overall very beneficial for the build, the conversions from Aether to Fire or Acid is a bit unlucky, but the pistols do 45% Aether to Vitality with Harbinger of Souls each, so not all the flat Aether from Spectral Binding is lost.
Everything else is just there to provide some support here and there and while not essential, it’s obviously very beneficial, like e.g. the gloves, as their Lightning damage gets converted to Vitality thanks to our pistols and therefore add a lot of damage to BWC.
PERFORMANCE
The campaign was a breeze, kinda nice to be able to walk 6% faster with ranged weapons now.
Crucible is very doable, just don’t try to facetank waves 160, 169 and 170.
Callagadra took around 20 minutes and I used a Bloodied Crystal in the other ring aswell.
Mogdrogen can be facetanked if you avoid the sunder most of the time, use Stormshroud Ointment and Elixir of the Dranghoul. It took around 4 minutes.
CONCLUSION
A tricky combination with lots of Vitality RR…
-20% from rings, -28% from Rattosh Devotion, -35% from Spectral Wrath, -30% from Thermite Mine
= -113% + either 20 from Tip the Scales or 35 from Agonizing Flames (they don’t stack)
…high resistance overcap and some increased max. resistances, 37% Life Leech (so Fire Strike to take advantage off of it) and only 4 additonal buttons to your mouse buttons make this a very enjoyable build.
If you have any questions, feel free to ask.
I am however still a beginner in this game, so any tips or tricks to improve this build are very welcome and much appreciated.
Thank you very much, I really hope you enjoyed this little overview. 
but unfortunately just the Fire Strike focused Gargabol Defiler is on a completely different level than a caster like that, even if it’s better optimized.