The Temple Guardian’s left arm unfolds a large parabolic mirror and fires a powerful beam of concentrated energy. Does DoT (Damage over time) and will damage anything in the beam (during the damage pulse). Skillful sighting upon an enemy can result in numerous monsters being damaged over time unless they move away from the beam.
Any enemies caught in the beam will take damage. Therefore it can be productive to target an enemy in the back of a mob. The beam will hit all enemies in between the Temple Guardian and the target, and if the target enemy starts moving around, the beam will follow it, slicing through all enemies standing in the way.
Choose Paralyze - Weaken - Annul for maximum debuffs to the target enemy.
Bronze mod Bundle may be a better choice as raw damage is probably more valuable than debuffed run speed.
Damage mitigation makes Gold mod Shelter the better choice for a defensive-oriented Temple Guardian.
There's no point in working to get the regeneration time lower than the duration of the beam (3 seconds) - you can only have one beam firing at a time.