That depends of the source files (its resolution) as well as all developments made.
IMHO, that's a normal speed.
Files are from nikon D750, 6000x4000, cca 25MB in size. Developments I would say some are basic and some not. Overall all photos have one preset over them and maybe a gradient tool or brush.
And what type of exported file are you saving, TIF/JPG, and if JPG what is the quality setting?
Exporting 6-7 25MB images with gradient and or brush work and other edits every minute isn't the best but not all that bad.
The Local Graduated Filter and Adjustment Brush tools will increase Export time. Try it for yourself with some images that have no Local adjustments. On my i7-860 system with SSD using 21Mp raw files it takes about 5 sec. without Locals and up to 15 sec. with Locals per image.
Catalog and pictures are od my ssd, and I export on ssd. Export setting are jpeg, 300dpi, resize to 8 megapixel, sharpening off. No other setting.
When using 'Resize to Fit' in the Export module it is important to add 'Output Sharpening' for the intended usage (Screen, Glossy, Matte).