There are two reasons why I didn't see this earlier: I used to play with friends on higher MPs with both my DH and WD. With the extra HP mobs have in groups, there must have been a lot of situations where I would kite a few mobs away from my friends, as they woudn't have the aggro, and it would take me so long to kill them that I would run out of discipline or mana and die quickly. So I always got the feeling that my characters were not good enough for this.
The other reason is that I almost doubled my discipline pool with my DH recently, with the Nat's set, so I think it makes a huge difference in high MPs. It just didn't cross my mind that I could ever survive and do okay in these situations. But you guys made me question myself, I tried it and was quite surprised.
So in a way, I was wrong saying Barbs did way better. But, I still think that they cost a lot less to gear up: 10mil vs 40 to 50+mil, for the exact same result.
Anyway, my simple and short post brought a lot of cool opinions and discussions. Hope you guys continue. It actually had a positive impact on how I see my DH and WD now.
I don't really like the term OP, as I don't want barbs to be nerfed. But I wanted to share my experience with barbs after playing a lot with my demon hunter, and after leveling all other classes to 60.
After paying more than 50mil on my demon hunter (I lost count), and about 40 mil on my witch doctor, I found myself having a difficult time in higher MPs. With my demon hunter, I have to kite a lot as soon as I reach MP4, and my witch doctor can handle MP5 quite well, but I run low on mana a bit after casting too many zombie bears, and I die a lot in MP6 and higher.
Anyway, I'm still working on gearing my monk and wizard: they can't handle more than MP3 for now.
As for my barb, I didn't put much gold on it, not more than 10mil for sure. And I can farm MP8 easily with a rend build. I tried MP10, just to see, and I killed the first pack I saw without dying. So, IMO, barbs are much more powerful than other classes, because they have huge buffs of DPS and defense, and it cost so little gold to gear. For less than 10mil, I can have a DPS of 190K with in game buffs, and still have lots of armor and resists, and a good amount of life.
I know my barb isn't that great, but I can still farm MP8 without dying.