Those are like my thoughts exactly! I don't like Rin's voice, even though I love the voice actor, I think he could've sounded a little... gruffer? Huh. I dunno. Like he sounded too boyish to me and in the japanese version he sounds like he's going through puberty with all those cute little voice cracks x3. Plus when I heard him I was like- Kida. Go back to Durarara!! NAOW. And Aido too from Vampire Knight.
And then for Yukio, at first it sounded like Izaya, Lelouch, all of those wonderful characters Johnny Bosch does. But then at least it was better than Yukio's.
Actually- I really don't like Mephisto's or Shiro's voice either.
As for the others- So far, I'm liking them. Like, Bon's voice actor I know will do a good job and Shiemi, Izumo, Paku, Shima, and Koneko all sound great. Even though they've only said like one line each. (Shiemi's is at the end of the episode in the previes for episode 4, as it isn't out yet.)
I'm dying to hear the voices of Shura and Amaimon~
So overall- I do prefer the sub but I think I'm going to watch the dub through, just because I get to watch the show again.