Not quite, a point of armor increases your effective health by 2,5% (Health divided by damage reduction from armor)
The formula for armor damage reduction is 1-40/(40+armor)
This also means that armor technically does not get worse the more you get it, but health gets more effective the more armor you have.
Generally you want to hit breakpoints where the value you gain from armor and health are equal, and since the attribute system in Supernova makes this easy to figure out, simply the amount of health and armor you have should be equal to what one point of attribute points give. So basically you need 2 armor per 100 points of health to make the most out of your attribute points.
Edit: Slight miscalculation, in fact, you need 100 health per point of armor, not every 2 points to gain the maximum amount of effective hp. At 4000 health and 40 armor, you have 8000 effective hp because 40 armor equal 50% damage reduction. 100 hp here increases your effective hp by 200 (100/0,5) and 2 armor also increases your health by 200 (5% increase in your base effective health, 4000*0,05). This means that you should aim for 100 health per armor to gain the highest and cheapest amount of effective health.