That's about what they are on a 'real' camera which will save the images at 250 or 300dpi.
Even on my D3x - 24Mp, full-frame - NEF images open at 16.8" x 25.2" (4032px x 6048px).
On a D3 - 12Mp, full-frame - they open at 11.8" x 17.7" (2832px x 4256px).
Plus by selecting NEF & JPEG, you're saving two versions of the same image to the memory card.
If you're going to open them in Photoshop anyway, there's no real need to shoot both - it's just using up more space on your card: if you need JPEG, shoot JPEG, if you need or want RAW/NEF, shoot that...