SAS4 Armour Calculation + is body fuelling worth it?

The purpose of this is to determine how much armour points armour and augments gives you, and whether you're better off just getting body fuelling.

To begin, here's a graph of plotted points and the fitted curves of armour(x) vs armour reduction(y):

https://www.desmos.com/calculator/aoejoqboe5

The curve is segmented into two parts, one before 5500 (technically 5500.694 but doesn't matter for most cases) armour and one after.

y = sqrt(x), 0 <= x < 5500
y = sqrt(x-5500)/5 + 74, 5500 <= x < 21125
y = 99, x >= 21125

I don't know if 99% resistance is the cap with the heavy skill set. I'll ignore the possibility that it is as its mostly irrelevant.

Basically you get two armour reduction boosts, one at 0 and another at 5500.

Now, on to the benefits of each type of defence:

Body fuelling:
- Adds defence to all three stats at the same time by simply adding more to tank with
- Makes dark minion less effective
- Scales with your health as you level up

Resistance augments:
- Makes medkits more useful as they give a constant amount (doubt this applies to loot drops)
- at 99% resistance you basically have 100 times your normal health, which you probably can't do with just health increasing skills

Personally the hardest part will be the fact that there are three resistances, and each piece of armour can really only add to one or two of them, so deciding which option to go will require all three to be considered.

I'll tackle this with a simple scenario, where you get hit by a regular zombie, a fire zombie and a poison zombie. They will deal 100 damage each, and the aim is to reduce the percentage of health you lose using your armour augments.

As far as I know 10 body fuelling on any piece of armour adds 25% health. If r is the resistance %, then your effective health as  result is multiplied by 1/(1-r). This amount starts out tiny, but after 80% skyrockets.