1) THF has no real use. TH2 is the best form of TH in terms of noticeable boosts, anything past that is all pretty much unnoticeable/unseeable boosts. So we're not even good for that beyond placebo effects.
2) We have no real DD capabilities, similar to a lot of lesser DD jobs, Except THF falls further behind than others in this Gap. Since 75 the gap between THFs power and the next best DD has widened much further. In this field, we don't ask to be top tier DD, simply to have the gap lessened.
3) Devs want us to be support class and "Control enmity" and as it stands THF has no real methods to "Control" enmity. 2 Abilities on a shared timer and no way to disperse extra Enmity does not a master make. So as far as the Devs "vision" of the job goes we even lack capabilities there
4) Over-all Lack of Uniqueness of the job, usefulness of the job. Right now the only thing keeping THF relevant is ignorance of Treasure Hunter, But once that becomes common knowledge I doubt THF will keep its head above water.
5) We're all disappointed by the BS Responses we got earlier, which basically to summarize tell us things like "Aura Steal is too powerful to separate from Steal, or Reduce timer", and "You can't have Subtle Blow because You melee for TH upgrades, and we feel that balances it", etc.
Sorry i can't go into more detail as i know its a bit hard to discern from these 5 points, but a lot has been discussed.