how to use volatility?

Hello, could someone explain me how to actually benefit from this mechanics? I am surely doing something wrong as this does not make any sense

1) I build up volatility while fighting enemies. When the fight is over, timer expires and I gain volatile power while picking up loot and moving to another encounter

2) cant stack it effectively against single target, so another mechanics that could add damage when you don't need it and is useless when you need damage the most (against uber bosses)