Are you sure it would be a mistranslation of the book? It seems that the commas, the repetition of the ~の, and finally the addition of そして in the last phrase, all are used to describe (unflatteringly, insultingly, mockingly) Dumbledore.
That ordinary, half-blood, muggle-loving Albus Dumbledore
Note: Albus Dumbledore is a half-blood, right?
Having those adjectives describe ally/partner/friend feels a bit weak to me.
Albus Dumbledore: that friend of the ordinary, the half-blooded, and the muggles.
although both are plausible and grammatically correct. I haven't read the original so I don't know what the speaker's intention is. Anyway, It reminds me of the famous line in Wizard of Oz:
You clinking, clanking, clattering collection of caliginous junk