Descent into Hell!!! Rarrr!...Well, sort of...

[Shelob]

Not always Fordim, Perhaps 'tis true that in longer tales the hero meets with a "now-dead heroic-yet-problematic figure from the past" but it's not always so in shorter tales.

Orpheus for one descends into hell (Hades for him though) and returns without meeting any who went before...

When Orpheus' wife, Eurydice, was killed by the bite of a serpent, he went down to the underworld to bring her back. His songs were so beautiful that Hades finally agreed to allow Eurydice to return to the world of the living. However, Orpheus had to meet one condition: he must not look back as he was conducting her to the surface. Just before the pair reached the upper world, Orpheus looked back, and Eurydice slipped back into the netherworld once again. (From Here)

I don't know how well that's applicable to Lord of the Rings...but it's still worth considering...


Another way to look at it could be that Frodo does meet a fallen hero, just one who's not died yet, and that this fallen hero is usefull...just not in terms of guidance. When one considers Gollum as the 'fallen hero' it almost works...he is from before, he's just not 'dead', and he doesn't give useful guidance but without him everything would have been for naught and Frodo would have failed...