Drafts do tend to be flatter in the feet than light horses. Was she worked so hard that she wore her hoof wall down to nothing? That is really odd because most drafts have excellent tough feet. Are you sure that she doesn't have something going on like Seedy Toe?
She is standing wrong now, but I can see that she is cow hocked, and she is butt high. I think that her shoulder is too upright to allow you to have the lift and hesitation you need for dressage. She could do low level dressage but nothing more than maybe 2. She also has a very short neck, even for a Perch, and this is going to interfere with her ability to flex at the poll.
Right now is not the best time to evaluate her. But, if you would take some very good (non cell phone!) photos of her feet- front, side, rear, and underneath- I would love to take a look and see if I can figure out what is wrong. What is most likely is she has a lot of side flare, causing her to hit the ground toe first. This will wear the toes down faster than the heels and sides, and will create the flat dinner plate feet.
Spent a whole hour today laying in a pasture, waiting for a sparkling vampire to show up. Alas, I woke up and looked over, only to find a mound of horse crap. Sigh.