Just bouncing some ideas around.

First the simple system:

A unit can take 1 point of damage before it is destroyed.
When a unit takes a hit it can attempt to save. To save a hit the unit must roll equal to or better than its Armor value on a d6.
Armor values can be one of the following: 2+, 3+, 4+, 5+, 6+, -

Assuming DR is the average number of hits it will take to destroy a unit, I would set DR as:

DR = 1 / Armor Divisor*

* 2+ = 0.17, 3+ = 0.33, 4+ = 0.5, 5+ = 0.67, 6+ = 0.83, - = 1

But what happens when I add:

A special ability that ignores armor. IE, a unit does not get to save a hit with Ignore Armor.

A special ability that gives a unit a second save. IE, a unit gets to save twice against a regular hit (once using its regular armor value and once with its augmented armor value if it fails with the regular armor), and once against an Ignore Armor hit (using its augmented armor value).

Assume that an Augmented Armor value can not be better than a unit's regular armor value but can be one of the following: 2+, 3+, 4+, 5+, 6+

Would you have Augmented armor modify DR as follows:

6+ -> x1.2
5+ -> x1.5
4+ -> x2.0
3+ -> x3.0
2+ -> x6.0

This is what I originally though but it weights Augmented Armor the same as Armor. Shouldn't Augmented Armor be weighted more because Ignore Armor is out there?