Basically this build uses a few core passives
Unforgiving: Fury does not degenerate any longer. Furthermore, the Barbarian gains 1 Fury every 5 seconds
Berserker rage: increases damage dealt by 20% when the Barbarian's fury is at 100%
Slaughter (level 28): increases damage dealt by 20% when the Barbarian's fury is at its maximum. (This could be the same skill as berserker rage)
Relentless: when the Barbarian is under 20% HP, skills do not cost any fury and damage (TL's Note: dealt or taken?) is reduced by 50%
The idea is that you just attack normally doing your +20% or +40% damage but once your health is below 20% you can chain as many resource hungry skills as you want without needing the fury.
To make it a bit safer you could add
Insane courage (level 31): When the Barbarian has under 35% HP, damage taken is reduced by 30%
To sum up +20-40% damage
80% Damage reduction when low on health (If the DR Stacks)
Unlimited fury use when at low health
This whole build would be so boring though. I mean why have a passive that requires you to not use your skills. I guess it means you can fill your skill slots with uber powerful cool down skills. Hmm could be a bomb in PVP.