There is a LOT of flex with backbar sets and monster sets and skills depending on what the other tank is bringing, the rest of your comp, and the fight you are taking.
If DDs do not have 7.1k pen on there own you will need Crimson Oath as back bar set and Arch Druids Deveric as monster set
Other useful skills is Blinding flare front bar for a passive Major protection buff. Also for high block fights such as Lucent Citadel first boss Defensive Stance is a great passive increase to block mit and cost reduction.