Copied from maxroll, bonespear endgame build:
Caged Heart of The Barber OR Caged Heart of the Malignant Pact - In general you may have better results with The Barber early on when you don't have the build finished, and better results with Pact when the build is closer to completion. The Barber may be the better choice for some encounters like Echo of Lilith and World Bosses as well due to its ability to Critically Strike and proc itself, leading to some reports in the community of 300M crits or more. But keep in mind that these encounters are a very small selection of the overall gameplay. Ultimately, you may want to stock two rings for different loadouts, if you're really min-maxing, or just pick Caged Heart of the Malignant Pact for a "best fit" scenario.