I'm working through Dawnguard DLC and I find it worth 800 pts. The vampires powers are fun to mess around with, but are kind of a pain to level up. Can't comment on the werewolf powers as I haven't been given the chance to become one (again). I'd say this DLC is worth the price and if Dragonborn has more to offer then that should be worth it too.
Healthfire doesn't seem seem worth it unless you are starting a new character for it.
<G>A Brother who always helps the widow's son; are you a traveling man too?<G> Addicted to->FE: Awakening