pruning viburnum davidii

I planted 3 viburnum davidii shrubs in a group about 8 years ago and they've been very healthy and looked nice. Just recently when I was checking my shrubs I noticed they were all covered in black spot s - similar to the disease you get on rose bushes. I've chopped them all down to stumps about 6 inches high as they were so unsightly (I've got my garden open to the public next month) Have I been too extreme? Will they grow back or shall I dig up the stumps and put in something else? In the meantime I've planted loads of cosmos and other tall annuals to disguise the devastation. Advice needed please.

On plant viburnum davidii