Irony is one of the core techniques used by Scott. Take for example Roy - a violent, commando replicant. But he is the one who saves Deckard's life. He is the one endeavouring to become more human. The motto of "more human than human" for the replicants is apt - they feel, and look out for each other, while the human society, who are actually human, do not, due to their dissociation with nature. Thus, it is ironic that the 'villian' and 'hero' can be seen as the opposite way around.