I'd say yes. Given Dialga's great special attack and slew of resistances, it can switch in and out no worries. Coverage isn't an issue either: you could use Fire Blast and/or Aura Sphere with Draco Meteor, and you'll hit everything for neutral damage (apart from Heatran with Fire Blast). This means you can free up a slot for Dragon Pulse, so you've got a STAB for power and a STAB for consistency.
DO NOT RUN ROAR OF TIME!! Over 2 turns, Draco Meteor and Dragon Pulse both do more damage.