When a Guardian uses their defensive stance, they are one of the most difficult classes in the game to bring down with any kind of attack. They can also switch to a frenzy stance which will increase their damage, but make them easier to bring down. They also have many group buffs like Battle Cry or Morale Boost that provide bonuses to their entire party.
The two primary feat paths that Guardians can choose between are Juggernaut and Tempest. Juggernaut contains an array of skills that boost their defensive abilities, while Tempest focuses on increasing the damage of their attacks, primarily with polearms.
Guardians who want to do more damage will likely favor the more reckless Tempest tree, but even those who want to improve their tanking skill as much as possible will probably dabble in the tree as well. Every Guardian gains access to a varied array of self-buffs that they can use to fit the combat situation they find themselves faced with. They can use an ability like the Bolster the Line buff when they face a strong, slow enemy, as it increases their maximum health at the expense of movement speed. Wall of Steel increases melee avoidance, but every time that they take a hit, their stamina will be reduced.