It's not a hard concept to understand. Generating enmity is currently a joke so why not give options for us to sacrifice our enmity generation and apply the resources towards other gains instead? Let us choose what is more important at each point in a fight.
Do we need more threat? More mitigation? More damage? Because right now the answer to all three is RoH spam which is really sad... The closest we have towards options is if we need mp for flash spamming, and that is pre-determined before the pull even happens.
Just want to take the mindless drone aspect for applying our combo's out of the system.