After a lot of thought, I decided to revise my soul knight class. Even if the spell was technically RAW, I felt it would be too powerful over all. So I tweaked it into something else:
http://micahblackburn.wordpress.com/2012/12/10/house-rules-classessoul-k...
I think that's a lot more balanced. The other version was powerful, maybe too powerful, and might lead to the dark side of the powergamer ;)