Thanks a lot for the advice! I ordered the Heliopan filter today and am very eager to see the results, and I admit I hope that wb will fix it most of the time because with Photoshop I end up with a 100mb tif instead of a 20mb dng :-o
Wb can fix it but I personally alway fix it in ps because then you can work in layers because sometimes the colour cast is higher(more noticeable) in certain regions than in others so then you have to use masks.
And there is also the fact that white-balance only checks if the whites are white it doesn't necessary mean that the other colours are good after correcting wb.
Which most of the time they aren't(if you stack) because the nd's give a stronger colour cast.