Virgin plane circling with an undercarriage gear problem

Landed safely...non-event really.

Were they just dumping/wasting fuel before attempting to land?

No doubt. Last thing you'd want to do is land a 'heavy' jet like a 747 full of fuel to last you to Vegas, with one of the landing gear not full down and locked.

The lighter they are the slower they can land the aircraft, allowing more runway to be used and being able to flare the aircraft for a little longer.

They were probably in a holding pattern at a low altitude with flaps deployed and all the landing gear deployed to create more drag. 

However, they can't have been very low on fuel as they were only holding for a couple of hours. Not sure they dumped fuel either which at low altitude would have to have been down over the sea.

Still, nice smooth landing.