Also the Wounds could be something like, do not roll on First Aid Table, until Last Wound Then As Normal.
1st Wound through lose 2D HtH
2nd Wound TQ -1
3rd Wound TQ -1
4th Dead
This would show the wounds taking effect.
For something like a Carifex,
Give it a TQ of d10, Morale d12
Armor of Hardened (does not lose a die for weapon types)
Tech Lvl 3 Armor (of the best the 'nids make)
Armor 5D (as cover is hard to get, and it is big)
Node (can control any Hive creature in 12")
Hard to Kill, Negates a Wound on TQ-3, (so it needs an 7, until it is wounded twice then

Physic Blast 2D Attack, Armor is Negated, Cover Negated, Range 12"
Venom Cannon, Med Gun 5D 1" radius
Claws, 2D each Claw; Massive Strength Ignores 1 Die of Armor
Guards (always take damage 1st)
TQ d8, Morale *
Tech 2 Armor, 3D
Claw HtH 2D Ignores 1 Die of Armor
Can Take 2 Wounds, 1st Wound Reduces TQ to 6, 2nd Kills
* As long as a Node is within range No Morale Tests
Wounds to Guard do not Cause Carnifex to make Morale Rolls.
So 2 Guards and the Carni, would get 11D rounded to 10D on Defense. 5d10, 5d8.
Ranged Attack would be 5D Med Gun 1" radius, or 2D Psyker Attack.
HtH would be 5D10, and 6D8.
Or something like that

Will have to sit down with the book, and look at the options allowed.
He is nasty and hard to kill, as he should be. But as you plink him, he becomes easier to kill. TQ Loss
Also Remember that Med and Hvy weapons make it harder to save on Hard to Kill.
One of these things could take on a large number of Fire Teams, the Manual says use Tanks whenever possible.
I like using the TQ for the Hard to Kill Roll, as it shows the creature is as wounds get in, losing the ability to fight.
Lee