Eventually got the RFE from NSC as follows;
The documentation ted is not sufficient to warrant favorable consideration of your petition/application.
.......
(please Note: the evidence already ted demonstrates that the proposed research employment has substantial intrinsic merit and is national in scope.).
Provide additional documentary evidence that, as of the filing date of the petition, you had a degree of influence on your field that distinguishes you from other scientists with comparable academic/professional qualifications. The evidence may include, for example, copies of additional published articles that recognized your research achievements. Similarly, evidence of official recognition conferred on your by government entities or professional organizations may also be ted.
Question: Is this a tough question or a routine question? Besides additional reference letter, related publication which is ted before the filing date, more citations of previous publication after the filing date. What else would be helpful in this case? Thanks.