Wanted to share some tech that I am using on my MSoZ Juggernaut. I was looking for a way to consistently apply wither + curses with a merc while maintaining good survivability and coverage. I think I have found a pretty good setup:

• You need a kineticist with Haste and Kinetic blast of clustering - they spam this skill and each attack hits 4+ times (more if it is linked with LMP/GMP)
• Have merc use Wilma's Requital - This will allow the merc to double-dip the haste buff, speeding up their attack speed. This also stops the merc from doing any damage, but this is actually a bonus since I only care about debuffs and this makes them reflect-immune.
• Equip merc with Abhorrent Interrogation - 25% chance to apply wither on hit

With the above setup, you should be getting upwards of 5+ APS with a fast wand, each of which hit at least 4x, resulting in fairly consistent application of wither. Stacking +attack speed or +cast speed (Wilmas allows both to affect attack speed) on the rest of your gear will improve your stacks and consistency.

In addition to wither, I have my merc use Anathema + curse on hit gear to apply despair (wand)/temp chains (glove implicit). With KBoC, the coverage is exceptionally good, so you should see the entire screen double-cursed pretty much instantly. Additionally, I have +30 life on hit on the merc's wand, which makes her essentially unkillable so long as she is attacking (other than one-shots)

Testing KBoC explosion overlaps

Apparently GGG changed KBoC behavior such that the secondary explosions don't overlap. This does NOT seem to be the case for KBoC cast by mercenaries. Here are some videos for comparions:

• My merc casting KBoC - notice all the explosions seem to be overlapping on the single mob
• Me self-casting KBoC - explosions are spread out and don't overlap the mob

At least based on the visuals, I'm inclined to believe that mercenary KBoC doesn't have any spread, so it can more reliably hit a single target, maintaining higher wither stacks.

Crafting merc wand

Crafting a wand for this setup is fairly easy, although it will take a couple of tries - all you need are two wands that have the correct influence (hunter influence for despair on hit). You'll want to use a wand with a 1.6aps base (carved, engraved, imbued):

• Roll one wand with the desired curse on hit - can either alt spam or use harvest reforge caster
• Roll the other wand with +30 life on hit - can either alt spam or harvest reforge life
• Use the recombinator with predictable recombination to get a wand with only those two mods - should be about a 7% chance to succeed
• Craft attack speed - you can leave the prefixes blank since the merc doesn't do any damage

My full gear list

For reference, here is all the gear I'm using on my merc. She hasn't died yet in T17s or depth 550+ delve, but I only just started using this full setup ( POB for merc):

• Cospir's Will for bypassing hex-immunity
• Abhorrent Interrogation for wither on hit, corruption implicit temp chains on hit
• Kaom's roots for stun/action speed slow immunity
• Perquil's toe for MSoZ dps - I annointed this with Corruption for +20% withered effect
• Kaom's binding for phys > fire incoming damage conversion
• Anathema for additional curses
• Rare ring with resists
• Fast attack speed wand with despair on hit / life on hit
• Atziris reflection for curse immunity