Here is the foundation for the most efficient level 80 tanking builds:
Age of Conan Feat Calculator | Guardian Feats

You'll note that several points have not been spent. This is two-fold -- some abilities need further testing (Storm Blade) and some are specific to what you're going to be doing.

More specifically, if you're an off-tank or have other people in your party taking damage and building vengeance counters, take Bloody Vengeance. Max it out by removing one point from Bleeding Dulling Blow.

For everyone else, the decision is between three primary Hate investments: Counterstrike/Anticipation, Storm Blade, and Volcanic Rage. These require testing, though my gut instinct would be Counterstrike/Anticipation, or CS/Anticipation and one point in Storm Blade (again by removing one point from Bleeding Dulling Blow).