I just noticed some odd behaviour from Organic Armor while testing mines and discovered something interesting. So, here is a correction on how Organic Armor works followed by a brief note on emissive armor.
Organic Armor Correction
It works pretty much as I stated before, however, once an organic armor component is destroyed, it stops generating points toward regeneration for the remainder of the battle. That means, if you have 10 piece of OA-III (30pt regen/turn) and 9 are destroyed, from that point on you only generate 30 points of regeneration! So, once you run out of built-up regeneration, it will take 5 turns to repair each component
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Also, Organic Armor is not automatically repaired outside of combat (although it should be). In fact, I find it very amusing, assuming I have at least 1 OA remaining, to engage colony ships and such and just sit in place will my OA repairs itself. Repeat until all your OA is back. I think OA should auto-repair at the beginning of each turn, but hey, that's just me.
Emissive Armor
Ok, works pretty much just like you'd expect. It is not cumulative. It is triggered before damage is delt to your ship (but not before it hits shields). This means if you have 1 EA-III and 10 OA, no weapon doing 30 or less damage has any effect.
However, remember how extra damage to your ship gets added to future weapon attacks? That's right, this can let weaker weapons piggy-back past emissive armor. As if it wasn't worthless enough. So, if you have a Meson BLaster (30 dmg) and a APB (35 dmg say), fire the APB first then the MB and you'll get 65 damage on the target instead of the 35 you get by firing the MB first.