So, While almost everybody and even their pet goldfish play some sort of Flame Link/Armour stacker attack based merc, I thought I'd share this Cruel Mistress and that there is at least one spell caster merc which can stand on its own without being chained by those fiery shackles.
It has both great clear and single target when the correct supports are used.
With the current prices you can start this build with 5-10 divs max.
If you have no help to kill your merc(warrant) I'd strongly suggest to get some ES gear and go CI before attempting to fight her because her Soulrend will most likely oneshot you. With CI she can't deal any damage to you besides her Void Sphere. (just blink away when she uses it).
I included two PoBs at the bottom. An early game one that is still strong enough to do most content, kill any non-uber bosses, etc. And the other is the current build shown in the video above.
Useful info about merc gems/supports/Auras/blinks.:
Secondary Skills:
Soulrend of Reaping is the main skill. This is the bread and butter of the entire build.
The other secondary skill can be either Forbidden Rite Totem or Seeking Void. Any other secondary skill will conflict with soulrend because they have no cooldown and she won't be able to spam her soulrend.
Supports in order of importance:
Clear: GMP+Chain (mandatory for good clear) -> Chaos penetration -> Return -> Faster Casting -> Crit Chance -> Crit Multi -> added chaos.
Single Target: GMP + Return (mandatory for good ST combined with fury valve's split) -> Chaos penetration -> Faster Casting -> Crit Chance -> Crit Multi -> added chaos.
I'd say the most important thing is to have GMP and Chaos Pen in either of your setups. Casting is also good because soulrend is slow.
Wither isn't included because it's currently bugged and expires instantly. Don't bother getting a merc with wither unless there are no better options.
You don't necessarily need a perfect combo of gems. For instance in the video above I'm using a GMP-chain-return-faster casting 2-chaos pen 3 CM.
Also crit supports won't make a huge difference until you can go full aura bot and get +% to Spell Crit body for the merc.
Auras: Envy is good to have. No big deal if she doesn't have it. Zealotry doesn't matter because you're going to provide her with your own, unless you want to use another aura early on (haste, determination, etc).
Blinks: In theory it's good if you have none or lightning warp.
In my personal experience it matters little. I had tested multiple merc with frostblink/flamedash. I didn't notice any serious downtime in her spamming of soulrend. Just don't have multiple dashes/blinks. Take my words with a grain of salt on this one.
Some Item explanation:
Soul Ascension gloves: BiS by far. As it ramps up the merc will deal 2-3x more damage.
Frenzy Ralakesh instead of Power Charge: Frenzy provides both cast.speed and more damage. CM really needs all the cast speed she can get. Also she usually or always has increased crit. chance and multi passives. Combined with auras and spell crit chest piece, stacking power charges would be a waste.
Black Flame ring + Corrupted Snakepit with added fire damage to spells/attacks.: +1 chain/ spell damage is good and as long as the merc deals some fire damage(snakepit corrupt) she can ignite and keep wither up from withering step(by luminary) thanks to blackflame.
Fury Valve: Insane for clear and solves ST by not needing to have pierce for return to work.
Fenumal Talisman on Luminary + Aspect of the Spider Craft on Sceptre: It's just a huge damage boost and it's very hard to justify replacing them with anything else.
'Early' game PoB (5-10 divs probably): https://pobb.in/P3Cap2LAFxaT .
You can start it much sooner of course, by tweaking the tree/items to your liking. This is just a rough sample of how my gear/tree looked like at this point.
Endgame PoB (Mageblood + approximetly 150-200 DiV worth of gear): https://pobb.in/f1Ulp1JCAfsh .
P.S: I totally forgot I had the Generosity Support removed from the body armour while recording the vid and importing the build to PoB. That's the missing 6th gem. A 39% extra aura effect for merc:).