One doesn't have to have an immortal soul to see visions. Plainly those who saw visions weren't impeded by this. :-)
Unbiblical?
Unbiblical. Scripture after scripture affirms that the fate of man is death:
Eze 18:20 The soul that sinneth, it shall die. The son shall not bear the iniquity of the father, neither shall the father bear the iniquity of the son: the righteousness of the righteous shall be upon him, and the wickedness of the wicked shall be upon him.
Joh 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
We don't already have eternal life, an immortal soul. Everlasting life is a gift of God.
Perish = apollumi - From G575 and the base of G3639; to destroy fully (reflexively to perish, or lose), literally or figuratively: - destroy, die, lose, mar, perish.
What about hell? Jesus spoke more about that than he spoke of heaven.