Cleared Skeleton King on Hell on my DH and stopped there for the moment. Interestingly enough, between my Nightmare run and up to that point in Hell, I found something like 2 rare rings. One was actually an upgrade!
Nothing up to that point in Act 1 isn't really more dangerous than Act 3 or 4 Nightmare. I did have trouble with some Mortar dudes though. One was Mortar Illusionist Reflects Damage and I had to pass him up. Just too fucking insane as a DH who can't really take a hit anyway, and the copies just soak up all the mid-range where I'd need to be and/or spread out so much that I end up in the line of fire no matter where I am.
Surprisingly the Skeleton King took quite a long time to kill. Maybe 5 minutes or so. I wasn't ever really in danger, but I guess I just had low DPS (~3700). Been back to using a variation on my slow/kiting build. I feel like DHs lack a nice big nuke/power up like Super Saiyan for Barbs, or Archon for Wizards.