Repetitive? Yes! But Dead Space is Dead Space, and the more the BETTER!
How Isaac and Carver survived the fall is unknown entirely - there is a dialogue at the beginning which states something along the lines of the planet wanted to keep them alive for some reason, perhaps to keep the narrative interesting.
Although redundant, I found Awakened FREAKIER than Dead Space 3 - thats my upside to the dlc.
I think the reason for this is because of the cultists and Izaacs slip into madness, and for some reason those skinny screamer aliens really freak me out too - and there are lots of them in Awakened.
I recommend Awakened for all Dead Space fans, it wont disappoint.
The bottom-line:
Yes, its redundant and recycled but its Dead Space nevertheless.
Its short, but it makes me want more at the end, which is a good
thing. Play it!