why is heartless good?

[Annie enjoyer]

I still can't see how she is better that darkhorse or gustbuster.

HL has a redundancy and few problems with her SA.

First, the effects are activated when the enemy has 3 debuffs or less than 50% hp (it has to be 49%, very annoying), but to inflict 3 debuffs you need a very specific combo or supports, if you are already hitting you don't need unblockables with Marie, she is a bit like Beowulf with the chairs.

I mean, if you lowered the enemy hp that much, you will not be needing unblockable.

Second, her second SA is just activated with the last enemy, inflicting 3 debuffs to trigger her first signature, this time being pretty useful.
There are 3 problems.
It last 20 seconds, allowing enemies with big hp to endure enough to outlast Hex, activating on death skills.

It is useless against regen, characters like valentine or dahlia can get it with marquees, so bleed is removed.
To fix this, we could make them permanent for 20 seconds. Valentine and dahlia are popular defenses, so this is not a niche case, also applies to No mercy.

Secondary to this, the effects are bad, bleed is not that good in general, for a variant like her, death mark could be better, busting her damage greatly at the end without special counters. (Except PW)
She also suffers from resistance, she inflicts 3 debuffs * 50% resistance, at least 1 of the debuffs will fail, maybe if she tries to inflict quietus 3 times before the other debuffs it would be enough to help her.

Force her to get accuracy is a bit hard, and as plus, her bonus damage is just for skeletal moves.

 

[Kheul]

You can't really compare Heartless to Dark Horse or Gustbuster as they fill completely different roles. But if you ask me which one would I pick if I only get to keep one of those I would definitely pick Heartless as I use her the most among them and I can easily find alternatives for the other two.

I use her solely for SA2. She doesn't get to fight 95% of the time. So I'm not going to make any comments on her SA1.

Her SA2 provides 20 seconds of HEX, QUIETUS and HEAVY BLEED. This is an insanely strong combination of debuffs, you get to ignore opponent SAs, final stands/blessings and you have a constant H.BLEED damage which totals up to 40% of their HP.

This goes through AUTOIMMUNE as well, as long as you don't inflict extra debuffs those three will stay. Her only true counter is when the opponent on the backline already has Immunity before being inflicted with her debuffs.

Accuracy has always been a really strong stat. Even if she inflicted QUIETUS first you still wanna have max accuracy on her to increase the general chances on all her moves and make sure the debuffs land.

Her SA2 is better suited for rifts, but still can usable in high streak PFs if you have high DPS.

She is not supposed to be used against very tanky last slots like Megalomaniac. She is a situational pick, I don't force her against the comps/modifiers where she doesn't shine.