I don't really see what's the issue with Hellbent. Aggressive decks generally end up without cards in their hands anyway. Turns out, Rakdos is the aggressive color combo. There really wasn't a downside to the mechanic, beyond you having more limited options. I also don't really remember a sweeper in Ravnica block to punish you for going Hellbent, but its been a while. I think the issue is that Wizards was a little conservative with creatures still in Ravnica, and Hellbent creatures didn't really give enough of a boost considering the fact you had to actually GO hellbent to get the bonus, which is a very heavy drawback in Constructed.
I also remember RUG being the best color combo, and that you always drafted Karoo lands in the format. So there WAS that. The format ended up being really slow.