I have been wrestling with PDD over two of my newest additions, a blue roan tobiano + sabino TWH mare and a palomino QH stallion (with markings that could go splash or sabino). The TWH mare, at least, has a sire -- it's her dam side that I can't come to a decision over. The QH? Well, that's a whole 'nuther ball o' string.
So, my fellow PDD sufferers: who else struggles with this affliction? *grin* I feel yer pain! :-)