As far as questions about the story:
 Spoilers! |
For possible twists:
1. Stross is so important to the plot. No wait, he's a useless psycho.
2. Ghost Nicole wants you dead, then she wants to help, THEN SHE WANTS YOU DEAD AGAIN!!!
And the "make us whole" bit:
Tiedeman said Isaac's brain was the only one capable of accommodating the marker's baloney without going nuts, so I guess that made him important to the necromorphs. As for why they needed him for that, or why they needed him to jam a needle in his eye, or why if they wanted him dead didn't Nicole just try to kill him every single time she appeared, that remains unsaid |
In short, the writing was serviceable, but the writers were so wrapped up in trying to keep the player guessing that they forgot to wrap things up properly. If I wanted to make an excuse for it, I would say that maybe you'll get more answers in the inevitable third one.
As for Isaac himself, he just doesn't do anything for me. He has a little more personality now that he isn't a silent protagonist, but there's nothing that really stands out about him. I think that's what they were going for, though: ordinary man in extraordinary circumstances.