The character has a lot of buffs. I was having a hard time with a 232 Mage shaman against him. Only time I could kill him was when he would recast spells early and burn himself to death, or I got lucky with the summon and could hit more then once a turn at 50ish percent with an aim buff. If the summon didn't turn on me and try to murder me lol. As far as I've seen, there are some serious balance issues with this playable story.

I found a really easy way to kill her, bring 2-3 ghouls around you and wound them until red bar, the mage will start to heal them, burning herself during the proccess, when she gets to red bar, a round of shooting brings her down. Did this with a 250 samurai with an assault rifle.

Same problem here.
The cultist or whatever that guy is can only be beaten with luck as it seems.

Every time he drops red, he pushes himself a full heal (around 100hp at that time).
Even if he is drained that is still +60hp.

As a shooter class (decker with pistol) I can not ditch out enough damage to actually kill him.
Not to mention his high amount of health (around 150?) and incredible evasion stats.

Forgot to mention: You can not run from him either since he has 4 actions and just comes after you and kill you.

A little math:
If he heals himself for around 100 as soon as he drops to 40/50 and damages himself by 40 in the process you need to churn out around 90 damage to get him actually killed in the next round.
In one round.
Alone.
With a pistol.

How is that supposed to work out?

Tried to avoid the guy and just went after the 3 people to save.
Did not work either.
You get stuck in the gouhls after some time and can not get all 3 before you meet the mage.
Maybe as an adept with speed buff but without you need a lot of luck i guess.

Finally I aborted the mission ad started all over again.
After 3 hours trying to kill or avoid this guy that was my only option left.