The Head Evolution is a very welcome addition, but there are some ambiguous combinations:
Bite: I assume your bite only applies to one head, that you can take it more than once, applying to a new head, and that if you take it twice for a given head you can make it str-and-a-half.
Trip: Its not clear if this would apply to all bite attacks?  Or only to a single attack.  (My inclination is that it applies to all bite attacks, similar to Rend, although a counter-example would be Poison, or Push).
Channel Resistance: Less a clarification, more of a question. Why require the Undead Appearance evolution for this?  It is possible (although unlikely), that you might face an opponent with Alignment Channel.