Another possibility for better evenness is Lightroom’s Flat-Field Correction, which is mentioned in this post too: Orange bleed at edges of scans! Need help!
On the other hand, you could just counterbalance the effect by adding some vignetting back into the image. Based on your posted jpg, it looks like it is possible with these settings. Other settings should be able to correct the effect in your raw files.
If you find your settings, you could save them as a preset and apply it on import.