You're going to need at least all level 60-75 characters to do this. I recommend running through normal once and easy once as well. On the easy play-through, grab all the simulator discs and follow my guide here
I would recommend using the simulator missions, specifically the VS discs to level up. Hulk with his rage boost destroys health, Dr. Doom is just an energy source and can deal more than his share of damage. Silver Surfer (when you get him) is invaluable when you get molecular mix-up (400+ damage at level 99) and Wolverine for his regeneration and bleed damage against enemies. These are the best characters to fight Doom as they can all beat on him and deal massive damage while maintaing a solid amount of health.
Before you vote negative, leave a comment. I check this pretty frequently and I'm more than happy to fix or update/correct this solution.