I never completely understood whats the point of this feature:
From game mechanics POV, it makes more bad than good. Battles take very long time and turn out to be rather boring when all ships under fire max out their mitigations and the action slows down. Also, it makes focus firing, target preference and related tactics useless. The player has two options to make use of his his DPS optimally: either focus fire and change targets when the mitigation maxes out (which is dull), or just order all his ships to attack whole enemy fleet (which is no tactic at all).
From realism POV, its even worse. The shields are supposed to weaken both in capacity and intensity as they take damage, not the other way around. Adapting to enemy weapons? This could be explanation, but it feels adhoc and artificial (like the whole mitigation thingy). Why then weapons dont adapt to the shields? Also, mitigation works even when shields are down, wtf? Also, it looks funny when the whole fleet is finishing off damaged ship with maxed out miti and the damage it does is quarter compared to the damage it was dealing when the ship had intact shields and hull.
I have modded the thing out (set it to 10% with no increase actually) and the game is better without it in my view. Battles no longer take eons (but they are still reasonably long, now its just matter of dps/hp ratios), and gameplay is more dynamic and one pointless parameter i out.
Your opinions?