Runecaster/Hierophant is quite an awesome build, especially with some of the domains that add spells like Disintegrate or Wail of the Banshee to your spell list or if you just start with an Archivist and have almost all spells available to you.
If only the epic bonus feat list of the Runecaster wasn't so bad. I always end up having to take a couple of epic toughness feats because I run out of epic spell focus feats (even non-bonus feats are somewhat broken for him, he can only choose Spell Focus: Cold or greater spell focus so I need to take all regular spell focus feats on my non-runecaster levels/before epic levels). I wish you had just added Great Intelligence and Great Wisdom to that list to make up for the dozen epic feats that he could choose but that aren't in the PRC.