I've read that on a website before. Its supposed to be the ability to astral project your consiness partly outside your body so you have a video game type of preseption. Also stuff like reading your openents mental paths and the like.
No, astral projection requires you to be semi-conscious, if not unconscious. I suppose a psychic vampire utterly adept at astral projection could astrally project while conscious but even then, they would have to constantly switch between astral and physical to defend itself, a huge weakness. They can't be in both simultaneously.
And mental shielding depends on the abilities of the vamp. Some would take alot more than that to stop there powers and even that wouldn't help you if there basicaly a jedi knight with a thirst for pysic energy.
Actually it depends on how stupid the hunter was. An intelligent hunter would, before hunting, make sure that they could shield enough to block against any psi-vamp they may come accross. A hunter would probably train half their life before hunting psi-vampires. I mean, you don't see US soldiers going into war with nothing but chainmail, they make sure they're sufficiently beefed-up before going to battle. Doing any less would be suicide.