Stone Flesh, Obsidian Focus, Signet of Earth, and Rock barrier do not work with Strength of Stone or with Runes of the Undead. Seeing as how all of these skills/traits increase toughness and the description of Runes of the Undead and Strength of Stone explicitly state that toughness will be converted to condition damage, I think is unintentional that these traits do not have the desired effect. If the stated goal is to increase build diversity I think it would be beneficial for these runes and traits to actually work.