First of all, I know that their skill set aren't complete due to talent tree only offering first 2 rows.
What I'm referring to is their core rotation, which revolves around spamming Shear to generate Pain and then using stored pain on Demon Spikes for DR or Soul Cleave for damage/heals.
It feels sort of like a poor man's Rage bar. Unlike the Warrior that has several abilities that give them different amounts of Rage as well as their melee attacks and/or being hit, the DH only has 1 real ability, Shear. They can also use Immo that gives them 20, but is on a 15s CD (and Fellblade if they get that talent) and it actually takes weight away from it because we'll be using that ability whenever it comes off CD whether we're fighting 1 target or 20 simply because of the Pain if gives. It's not intuitive or fun.
It's a very VERY plain and mediocre resource system. Was hoping we could get a 2 level resource system like DK's RP and Runes, Monk's Energy and Chi, Ele's Mana and Maelstrom, Rogue's Energy and CP, etc.
Havoc suffers from same problem, but at least the random amount of Fury DB generates makes it for a bit more fun and intuitive then just a static 10 Pain gain that Shear offers.