The tooltip erroneously claims that the damage resistance is 10% per skill point, the actual value is 12% per skill point. In Borderlands, no amount of damage resistance offers immunity to damage, rather, the % value reflects the increase in effective hit points (shields and health). This means that an enemy must deal 12% more damage to Brick per skill point in Juggernaut (while its effect is active) order to remove the same amount of hit points from Brick.
The effect of Juggernaut can be considered equivalent to a temporary shield and health increase of +12% per skill point. However, this increase is separate from actual shield and health increases, and thus stacks multiplicatively with them. It also amplifies the potency of hit point regeneration effects because each hit point recovered requires more than 1 damage from Brick's enemies in order to be lost again (assuming the damage is taken while Juggernaut's effect is active).
+(12...60)% Damage Resistance
- Since Juggernaut essentially makes each hit point Brick has count for more against enemy damage, it effectively increases the power of hit point regeneration effects such as health regeneration and the shield regeneration from Unbreakable.