Movie Summary
This boss has a higher health pool compared to other naxx bosses, making this another endurance fight. From a shadow priest's point of view, endurance means mana conservation and regeneration. This means that Dispersion glyph and frequent SW:D use are vital to this fight.
Also don't be afraid to dps outside of shadow form. Sometimes it is not wise to waste an entire GCD and mana just to shift into shadowform.