I have a conc barb, my probablem was while I was building I didn't think to use the proper synergies except for Battle Orders, since I started out thinking I would make a BO barb. Though, at the same time it isn't very viable to use all the synergies, because you need 20 in Bash, 20 in Berzerk and 20 in Battle Orders, (and Concentrate, but that goes without saying), thats 80 points, that means one of the main purposes of concentrate; higher def and being harder to hit, can't be augmented with 20 in Iron Skin.
A good mix for a conc barb might be;
20 in Concentrate
20 in Battle Orders
20 in Iron Skin
20 in the mastery of your choice
10 in Berzerk
5 in Bash
I'm using a Metalgrid amulet too, and lifetap dracul's gloves, and two life leech rings. Basically not even Hell Baal can hit me, or damage me. However, I can't really dish out any viable damage unless I switch to my Berzerk with right click, but switching from Berzerk and Concentrate is, letting your life recharge from leeching and lifetap while you're using concentrate and not being hit back, and quickly hiting with Berzerk to wear the enemy down, and switching back. As long as you're swinging your weapons with concentrate, and you have good enough gear, you can't be hit at all.
EDIT: And if by BvU you mean Barbarian versus Ubers, well, the lesser Clone ubers yes, but I tried Uber Tristram with my Conc Barb, and wasn't able to survive to get close enough to start swinging, I lost my body, left game to re-enter, and game was full until ubers were dead and I couldn't get a second chance to try.
...but the moral is; the weakness of conc is in needing to be close enough to attack, and switching from one enemy to another makes you briefly vulnerable when you stop to aim at a new enemy.
A good mix for a conc barb might be;
20 in Concentrate
20 in Battle Orders
20 in Iron Skin
20 in the mastery of your choice
10 in Berzerk
5 in Bash
I'm using a Metalgrid amulet too, and lifetap dracul's gloves, and two life leech rings. Basically not even Hell Baal can hit me, or damage me. However, I can't really dish out any viable damage unless I switch to my Berzerk with right click, but switching from Berzerk and Concentrate is, letting your life recharge from leeching and lifetap while you're using concentrate and not being hit back, and quickly hiting with Berzerk to wear the enemy down, and switching back. As long as you're swinging your weapons with concentrate, and you have good enough gear, you can't be hit at all.
EDIT: And if by BvU you mean Barbarian versus Ubers, well, the lesser Clone ubers yes, but I tried Uber Tristram with my Conc Barb, and wasn't able to survive to get close enough to start swinging, I lost my body, left game to re-enter, and game was full until ubers were dead and I couldn't get a second chance to try.
...but the moral is; the weakness of conc is in needing to be close enough to attack, and switching from one enemy to another makes you briefly vulnerable when you stop to aim at a new enemy.