AoS Alternatives to constricted summoning

[Killer Angel]

We count Kroak as 10 wounds.
With "only " 7, he's 50% dead... but also 50% fully healed.
And given that Kroak can reroll dices, the percentage goes in his favor.

 

[Bainbow]

We count Kroak as 10 wounds.
With "only " 7, he's 50% dead... but also 50% fully healed.
And given that Kroak can reroll dices, the percentage goes in his favor.

On the other hand, counting him as 10 Wounds is too much because he can die from only half of that if you're unlucky. I see the 50% chance to heal as something like what the Slayers have where they have a 50% chance to ignore all damage, it's just an ability.