I also have a V700 and have had the same problem. The real truth (I believe) is that the V700 doen't have the DMax that Epson claim and struggles to pull detail out of shadows.
I did a lot of testing using the Epson Software, Silverfast SE (with Multiple Exposure), Silverfast AI and Vuescan. The Epson software couldn't render the same quality as Silverfast and didn't give control over the advanced scanner functions.
Silverfast was much better than the Epson but the Multiple Exposure caused serious fringing around edges with high contrast. Shame really because it did pull out more detail. I also tried a lot of test scans with the Multiple Sampling option. This did reduce noise and get more shadow detail but the problem here was the length of time the scan was taking. This was causing the slide or neg to heat up and shift in the carrier and as a result the software couldn't line up the multiple scans. The final image was OK in some areas but in others way out of focus with a ghosting type effect.
Vuescan didn't give as sharp a result as Silverfast BUT the Multiple Exposure works with less fringing (I suspect the fringing is caused by a low quality lens in the scanner). The Multiple scanning is much better and did capture quite a bit of detail in the shadows. Given the limitations of the other packages I found this to be the best.
Just for the record, I think the optics on my V700 are quite poor and the results are soft. I do use the Better Scanning slide/film holder which does produce a better result than the Epson holders. I still believe the optical resolution of the scanner is way less than Epson claim and is probably nearer the 1800ppi level; I just can't get it to resolve detail in the same way my Minolta 5400 could.
Final tip (sorry for the lengthy post), have you tried turning you negs over when you scan them. I found that when scanning some of my slides I could resolve more detail in shadows when the slides had one of the faces down to the glass. The other side of the slide would produce much more contrast and less detail.
Good luck.