But despite another big backing at Earls Court, they were sent out of the tournament by the ever-improving USA, who seem to have finally found the key to Olympic success.
They have made nine failed attempts to strike Games gold and, after losing out to Brazil at Beijing 2008, they turned to the all-conquering coach of their male counterparts, Hugh McCutcheon, to head up their squad.
The move has worked wonders with the New Zealander implementing an all-action style not previously associated with the side, and tonight's victory was the perfect showcase.
In Destinee Hooker and Foluke Akinradewo, they have point-scoring and blocking stars, with Jordan Larson dissecting them down the middle at will, often working off the reception of libero Nicole Davis.
The one downside was the absence of knee-injury victim and retiring captain Lindsey Berg but, with a rest day tomorrow ahead of a semi-final against Italy or South Korea, she may still have a part to play.
Her team-mates coped admirably without her tonight, though, with the usual names at the heart of the action.
Akinradewo, Larson and Hooker contributed a combined tally of 42 points, but that is not to say they had it all their own way.
They were on the brink of victory for a considerable period of time in the third set but some wonderful resilience from the Dominicans kept them hanging on.
Castillo was as determined as she has been throughout the tournament, chasing every lost cause until it was definitely gone, while Prisilla Altagracia Rivera Brens scored 15 points up high before the end finally came with a 25-14, 25-21, 25-22 win for the USA.