Calculation of void monsters power (1 Free ability?!)

Introduction:
The hypotheses is that there is a powercreep in splinterlands.
To prove this we need a way to quantify the monster power.
This is a work in progress:

• part 1 (melee)
• part 2 (ranged)
• part 3 (magic)
• part 4 (shield)

This part is about quantify the power of void monsters.

The power of void monsters:
Magic attack damage gets halved (rounded up), except attack 1 which deals 0 damage. (same as shield)

Let's assume you can predict quite well what the attack type of the oppenent will be.
That you will use void monsters against 70% magic damage, so the monsters take around 35% less damage.

The health of melee monsters is rougly the same as the mana cost.
The power value for shield should be -0.4 per mana.

With shielding we learned this is only true for low mana monsters, void is only available for high level monsters.
So a Unicorn Mustang (8 mana) should have slightly lower stats than Undead Rexx (9 mana), right? RIGHT?!

The rules to calculate monster power so far:
Basic stats:

• 1 health is 1 monster power.
• 1 armor is 2 monster power any additional armor is worth 0.5 monster power.
• 1 Speed is 0.5 monster power.
• 1 attack is 0 monster power,
• 2 attack is 2 monster power,
• 3 attack is 3.5 monster power any additional attack is worth 0.5 monster power.
• Rare monsters are worth 0.5 and Epic monsters 1 more monster power.
• Neutral monsters adds 1 monster power for flexability.
• Ranged monsters are worth 2 additional monster power.
• Ranged monsters are worth 4 additional monster power.
• 1 mana cost is roughly 1.4 monster power

Ability:

• Shield, 4 - 0.5 * mana cost, free from 8 mana.
• Void, 4 - 0.5 * mana cost, free from 8 mana.

The sample size get smaller for abilities.

Cards to mention:
Unicorn Mustang i don't know when it will be out of rotation, but i grabed one from the market, just to be sure.
All monsters with void are above the normal power curve.

Final thoughts:
I think all monsters have abilities naturally from a certain mana cost!
For shield and void this is 8 cost.
Let's check this for a ability with a decent monster pool next. (flying?)