No it is not save to assume anything. As a practical matter, however, they will issue and RFE eventually. it takes longer then 12 months to get the RFE from VSC. It really does. The team of officers working on U visas is very small. If you do not have an attorney representing you, find one. Do not do it on your own.
A request for evidence is not always sent on a U Visa. Often times, it is not requested. In my experience the Vermont Service Center has been taking 12 months-15 months to adjudicate the U Visas. If you think that yours is caught in red tape, you can call the Vermont Service Center and ask them. They are very helpful. Good luck, and keep the faith.
This advise does not create an attorney-client relationship.