I'have just tried the 2nd Genesis mission for the 4th times, on normal.
1st, quite at the beginning you are given the choice to help def Nihilon or yourself. Great, it is a non-choice. If you choose to help Nihilon, he is already besieged and the enginners pop so close to the battle. And with the so-limited resource, you have no time to build defenses there. Lost 2 attempts because of this. If it is truly supposed to be an option, it does not work. If it is supposed to trap the player, I do not see the point.
Now to the difficulty, I have seen a video at "much harder" difficulty, but guess what ? Things does not happen the same in my game.
I built up the def at the choke point, and hey, when a 1st army arrives she just past by my defense and go take points beside.
And when the army arrives to attack me, it is huge, really huge, I have same kind of def as in the video but they are just crushed.
Not sure what to do here, what is the trick ? Has something changed in a recent patch that make this mission so difficult ?