Demon Hunter is underpowered as a class. Most of its gimmickey utility was nerfed or revamped in some way. The class needs a review itself, and maybe new features. The problem of it only comes because Soldier, as a class, offers them nothing to back up their power, unlike let's say, Spellthieves, who have bonuses to Evade/Evasion from Rogue, and even further with their ability to snatch spells and overbuff themselves.
I don't quite want to bicker much about it because the problems are pretty apparent when you play it in the game atleast once, against any other enemy setup, and you get a bad time even against NPCs. And what I think it could solve the problem is adjusting the stances to give statistics to back up what they needed, status wise, like this:
Reaver Stance - While active, grants the Demon Hunter (10 * Rank) Hit against enemies within 1 range.
Cobra Stance - While active, grants the Demon Hunter (10 * Rank) Evade against enemies who are slower than you.
Desperado Stance - While active, grants the Demon Hunter (10 * Rank) Critical against enemies beyond 1 range.
Matador Stance - While active, grants the Demon Hunter damage reduction, based on the HP difference between you and your attacker. (1% per 2% HP difference, max. 5 * Rank%)**
If they have 100%, and you have 90%, you gain 5%.
If they have 100% and you have 80%, you gain 10%.
(Note that the gimmick is that if you're not spamming their HP percentage down with Bellowing Stag and Cursed Wounds, you'll make a better use of this. Since Cursed Wounds don't affect the enemy's HP percentage, for reducing from their maximum HP right beside the damage. Koonai smart mechanics.)
Everything presented above will also probably be halved if Demon Hunter is not your main class. (Even though I don't wish for this, if we're buffing Demon Hunter's stances. But depends on what people want, I guess.) So! Is this a fine suggestion? I'd put more about Reaver and Combination Fighter, but there's already a thread running separately.
Now salt and whine about how broken those are to your heart's content. Be free my children!