That's solid, though TFS, Spriggans, and Night Mother's Gaze are also good choices. With dungeons, your tank should be providing at lease some penetration such as from Major Fracture and Breach from Pierce Armor, so you don't necessarily have to be at the penetration cap by yourself.
I run 5 piece hundings and 5 piece spriggins with stormfist shoulders and head. The stormfist gives some needed stam recovery and the proc synergizes amazingly witg stsm sorc. Since switching my numbers and dps have all gone up. I use two daggers personally. Bow backbar obviously.