The first time I use the Barbarian was this year. I had some relatively good gear, and a fairly high Concentrate skill level..I went in and killed Duriel, using around 10 Full Rejuvenation potions or something..he was far easier than I expected.
its easier when you stack up on life leech and have a half-decent weapon to actually leech the life. I usually did just that and it worked too. having just 2 sigon's items you get the 10% life leech needed for most bosses.