I have noticed my vampire lord has been stuck in stage 2 vampirism, for what ever reason he will not advance to stage 3 or stage 4 no matter how long I go without feeding. I can verify this by checking my active effects i.e. the powers I have and my weakness to fire which stays at 50% (should be 100% at stage 4). Also I see npc vampires that have a bat face (most likely a stage 4 feature) that my player model never gets. I hope this is a bug because i want the new badass stage 4 vampire face!
http://imageshack.us/photo/my-images/16/imag0055p.jpg/
*On a side note I was a stage 2 vampire when Harkon turned me into a vampire lord.