The final ability for Summon Greater Undead appears to be summoning the incorrect creature.
Based on the description of the feat, the summoning progression is as follows:
Level 9: Mummy warrior
Level 10: Spectre
Level 12: Vampire rogue
Level 14: Greater bodak
Level 16: Ghoul king
From what I understand, the ability should consider total caster level, up to level 15 - making the Greater Bodak the most powerful creature summoned. Using this on a character with a total of 14 total caster levels, I was able to summon the Ghoul King (below).
Since it looks like this may need some tweaking, I did want to see about a potential change - as noted. . .
Here!