Nothing wrong with just 2 connectors on reference card, as I said above they can provide all the power that card needs.
There is when AMD themselves have to warn people about using the right PSU to avoid problems.
http://www.hardocp.com/image.html?image=MTM5NjkxNDM2NHhtamg2eEhLbHdfMV85X2wuZ2lm
http://www.hardocp.com/image.html?image=MTM5NjkxNDM2NHhtamg2eEhLbHdfMV8xMF9sLmdpZg==