Huh! Honestly, I've never just looked up Hellbent cards on Wizards, until you made your post. Some of them, and the cards you mentioned, are pretty dang playable, not to mention cheap- seems hellbent is obscure enough to be inexpensive
Which certainly suits me, as a mostly budgety builder!
When I was ordering Rakdos, I also picked up a couple
sire of insanity, as inexpensive as they are- honestly, I wouldn't use it- for the same reason as a couple other cards you mentioned- in this particular iteration because of the cost. The card draw from
avaricious dragon,
asylum visitor,
sin prodder, etc, is pretty inefficient if you can't cast them before discard, which is what makes the multiple cheap dragons mixed with ramp work so well for casting multiple creatures on multiple creature draw turns.
But hellbent is seriously intriguing me. I think I'm going to build and playtest a hellbent avaricious deck on untap- if it's doable on a budget and is enjoyable, I may splurge and have a third deck to share my avaricious dragons with ^^
Thanks for the card ideas man, hope you'll have some more input when I've got a test build up