OP, I appreciate you taking the time out to make present your ideas in a well thought-out post. I do like the job idea... but, unfortunately, a job called "Vampire" doesn't feel like a good fit for this game. Your ideas can work for Blue Mage, though.

If you replace the Whip weapon with a Fork, and you replace anything referencing "blood" to "Gourmand", you basically get Blue Mage from Final Fantasy 9: http://finalfantasy.wikia.com/wiki/B..._Fantasy_IX%29

This is what that title's particular Blue Mage looks like (cosply pic, not mine, but accurate):


Blue Mage in Final Fantasy 9 did not regain HP from eating enemies... so those type of abilities you presented may need to change... but overall your main idea is still in tact.