Ultron mode seems to be best for Mayhem boxes. Averaging 2-3 per run. Last go netted 5. Woot!
- edit - ^ Don't forget to see the GLF quartermaster in hammer bay. He gives you a device that will gain rep while playing every 24 hours. Its slowish but it all helps. I've never raided, and I just used those and the GLF dailys and weekly and it took a few weeks to max.
What's the device called? I don't remember getting anything from him after talking to him.