I'm afraid the particular idea presented in the OP would be... OP lol.

I could see groups "requiring" this class/job for content. That's never good.

However I could see these abilities being spread about to other classes/jobs. This could make more support/hybrid jobs similar to how BRD functions. BRD lowers its DPS to support the party, well another job could lower its own DPS to increase an aspect of the rest of the party too.