I'm fairly certain that I'm not the only one that knows of this, but I'm also fairly certain that I'm the first one to post on it.
1. Go talk to Fortunata to raise yourself to Relentless status.
2. Accept a mission from a contact.
3. Go talk to Fortunata to lower yourself back down to villainous status.(You can go higher, but this level makes running through the missions faster.)
4. Do your mission. You'll end up with the normal difficulty mobs, but the hardest mission payout.
Pros: Faster XP
Cons: Infamy gain is slowed due to constantly changing your rep. You will still be cutting a profit, but your gains will be slowed. Also worth noting is travel time. Once you get travel abilities, this strategy becomes noticably better.