I've modified a WeakAura that tracks Active damage reduction. It includes all externals (Hsac, Pain Supp, Guardian Spirit etc.), all class specific defensive abilities, all Tier 10 4-piece set bonuses and all major on use tanking trinkets (Sindragosa's Flawless Fang, Juggernaut's Vitality, Corroded Skeleton key etc.).
Need help: to further improve the functionallity I would only want the auras to load when they have been used by - or casted on - a player marked as TANK. Please hit me up on Discord (senshuken) if you have a solution for that.