User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-5593616-20131003192220/@comment-3146930-20131007010045

Well anyway, if that link is reliable, here is the breakdown:

Percy: 18 Chapters=23% Annabeth: 20 Chapters=26% Leo: 8 Chapters=10% Hazel: 12 Chapters=16% Jason: 8 Chapters=10% Piper: 4 Chapters=5% Frank: 8 Chapters=10%