User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-4515675-20121020161042/@comment-4531192-20121020225822

Considering there are governed books in the series and each book has three to four narrators, some characters are bound to narrate more often than others. I don't see a problem in this as long as the narrators are well chosen for each book and the choices do not decrease the fluidity of the storytelling.

As to the minor spoiler on Rick's blog - like Dark already pointed out - it does not confirm that either Percy or Annabeth will be narrating in the next book (Which I hope they will not as that could potentially make the narration jump around too much).

And as to Rick favoring the Greeks, I can see what you're saying just by looking at how four out of the seven heroes are Greeks. Of course seven is an odd number and so everything, but he could have made the last hero different from the others; maybe make him/her Macedonian or something.