Hey guys, I just registered, for now I'll only be in the Claymore area, because it's my new favorite anime, but maybe when I see some more animes I'll start popping up in other sections of the forums.
Anywho, back on topic.
Firstly, to answer the original question of this thread. I think Raki is quite a vital part in the story. Even though physically he is pretty much useless, he has had a very large mental impact on many characters.
When Clare was fighting the Yoma in the Great Cathedral and was about to Awaken, he still clenched onto her and said "I want to be with you forever." Were those not the same words that Clare told Teresa too? This was probably why Clare mustered the power to revert back to Human Form, because she had already given up and said it was useless at that point. What would have happened if Clare awakened?
Secondly, I have a hunch that the only thing that's keeping Clare going now is the promise she made to Raki. I believe she knows that she's no match for Priscilla for now, so she is focusing on finding Raki and staying alive like she promised. Maybe she would have just perished if not for that promise?
Lastly, look at what Raki is doing with Priscilla. Even though it is speculated that she does not feel for Raki or "care" for him, she still follows him and it was made apparent she hasn't eaten guts in years. Who knows, maybe Raki may be able to change Priscilla before her fated showdown with Clare.
Spoiler for Storyline:
I noticed by reading the later chapters of the manga, Raki has gotten experience in swordsmanship, since he took out that Yoma that Priscilla pointed out.
However, if you recall what the parasitic "needles" that the fusion of Raphaela/Luciela did, I am curious as to what will happen to Raki, and if he truly does have some kind of power in him. My way of thinking is this: Beth got stabbed by a massive needle and was consumed and awakened, while Raki was hit with three(?) of the very small ones, however I believe the effect will be the same. Considering that Beth was made into an awakened in a matter of minutes, and Raki, being only human is resisting the effects of three for so long, could hint that he has some hidden powers. Besides, I am curious what will happen to him. You saw how fast Beth awakened from the needle, Raki is only human, it's only a matter of time before the needles effects kick in, and I doubt the organization is fast enough to remove the needles, and I doubt they will since it's just another "experiment" to them. I wonder what will happen to Raki? Perhaps since he is human he will gain some Yoma powers.
Just something I had on my mind and wanted to put out there