Hopefully more information will be given about him in future serials since I know he did not actually die at the end of Genesis.
Think of Davros as the Doctor Who version of South Park's Kenny. He dies in every story he's in, but always comes back somehow. It's rarely explained how. We just accept it.
As you're working your way through the classic era, you may notice the same thing happen with the Master (mostly Anthony Ainley's version).
Rory and Clara only continue that proud tradition.