Honestly, Blood Gauge could go and make Bloodspiller and Quietus into 25s CD with shared charges.
Builder/Spender gauge don't have a place on every single job, and on DRK it could be completely removed without changing much if anything to the way the job plays. I'd even say this would give some breathing room to introduce or reintroduce other mechanics or approaches to the rotation. MP is the gauge of the DRK, it is enough, just focus on this.