You poor poor man. If you think 400 is bad, try 1100 images with a three day turnaround.
I shoot for some athletic women websites and hooking up with the models is sometimes a quarterly thing, but I need images for update every two weeks, thus the butt load of images taken at one time, not to mention the video shoots as well.
I haven't been able to get an clean up action to work properly, which taught me a valuable lesson, make sure you've got a clean "canvas" to light paint with. After going through close to 2000 images in one week, I realized it can't ever happen again.
I stop every outfit or set change and clean my lens. If I'm outdoors, even more so.
If anyone has an effective action that will heal, clone, mask, whatever a specific pixel area on more than one image in sucession, my kingdom if theirs. It would be a life saver. I've talked to dozens of photographers in my field, and they all have been in the same boat, a boat which has nearly sunk before because of a dust spot or other anomoly on 1000+ images from a weekend event.
Good luck, I hope someone comes to your rescue.