There are many, many people who truly believe that Raki is useless... I am not one of those people.
If Raki saved Clare's life and is her only purpose to live (besides killing Priscilla), how can he be considered useless? I admit, he's extremely annoying at times, but he's not useless. He represents humanity and what any human would do in his situation. People say "I'll beat the hell out of those monsters or this ain't nothin'" and all things high and mighty when in the end, it'll be just as Raki said, "I'm all talk and no action." That's just the way it is. Look back on all the things Raki did and ask yourself, "If he didn't do this..." I'll give you mine, "Without Raki, the protagonist Clare, would've died in episode 4, then where's the story we all know and love?