Hmm. Fixed those two. When you use spells, your DP for the day goes down accordingly. As for the 9th level spells... Well, you can only use two a day at max level, and by then you've sacrificed 3 levels to get that (That really isn't all that much though...). And the 9th level domain spells generally aren't that good (InB4Uberspell). But I could still slow the progression of spell level gain.
Also keep in mind that only the upper-level deities can even give rise to such a scion as to be capable of casting these.... And even then only those children that can survive to Near-Epic Level gain access to them... Hmm. Cue contemplation.
Good points. However, balanced against other bloodlines, these are pretty powerful, and considering the number of domains, versatile.