When killing the blade Nulgath gains a damage boost so it is preferred to not kill the blade too often, just right before he nukes the lobby would work. The blade nukes every 45 seconds so it is preferred for the DPS to focus on the blade if it is still not dead by 30 seconds.

Class Enhancements Consumables Extra Information
DoT Elysium/Wizard/Vainglory Sage/Malevolence Elixir + Potent Honor Role is to focus on nulgath, if not potted may need to focus on the blade at 30s.
DoT Elysium/Wizard/Vainglory Sage/Malevolence Elixir + Potent Honor Role is to focus on nulgath, if not potted may need to focus on the blade at 30s.
LR Arcana's Concerto/Wizard/Vainglory Sage/Malevolence Elixir + Scroll of Enrage Role is to loop taunt nulgath with LOO
LOO Awe Blast/Forge/Absolution Body/Divine Elixir + Scroll of Enrage Role is to loop taunt nulgath with LR

Alternative Comps

Class Enhancements Consumables Extra Information
DoT Elysium/Wizard/Vainglory Sage/Malevolence Elixir + Potent Honor Role is to focus on blade. Alternatively you can leave it at 50% hp and wait for your AOE to kill it.
AP Valiance or Ravenous/Forge/Vainglory Fate/Destruction Elixir + Scroll of Enrage Role is to loop taunt nulgath with LOO.
LR Arcana's Concerto/Wizard/Vainglory Sage/Malevolence Elixir + Scroll of Enrage Role is to loop taunt nulgath with AP
LOO Awe Blast/Forge/Absolution Body/Divine Elixir + Potent Honor Just keep buffs up and focus nulgath.

Alternatively DOT can swap to AF or VHL if not possible.