How can I remove photos from an iPad Min without having to restore it?
What you ask it trivial on iOS 9. Enable cloud photos in iCloud settings if you haven't already. Once it's synced, turn of the library. 

Select Remove and you are done. 

If for some reason you can't or won't do that, connect to a Mac and you can use Image Capture app over USB to bulk delete. I suppose a PC version of the tool would exist, but that's not my area of expertise. 

Also, you can select entire moments to delete on iOS 9 so even the manual method isn't a 1 to 1 tap to delete operation.