Please see https://www.wowhead.com/guides/vigilant-guardian-encounter-journal-boss-abilities-raid-loot for full information on this fight.

Brief Tactics

Three phase fight - an add phase and two boss phases.

Phase 1:

• Kill regular adds to activate big adds.

• Dodge stuff on floor and stay a bit spread out.

• Use the shield from big adds (yellow circle around them) during Exposed Core (when boss gets to 100 energy). 

• Use the bombs from the big adds and throw against wall where the boss is stuck (extra action button - make sure it throws!).

Phase 2:

• Face boss away from the raid (frontal) and taunt swap at 50 energy (pneumatic impact).

• If you get Matter Dissolution debuff, run far away - orbs appear in a circle around the player, slowly moving towards where the player was when they appeared (player runs back to group, through gaps between orbs).

Phase 3 (15%):

• Soft enrage.  Raid wide damage.  Bloodlust, Healing CDs.  

• Make his health hit zero before yours does.