Daphnes don't like to be dry, they just like EXTERMELY good drainage. If the leaves on yours are turning brown to black and hanging down and dropping off, they are indeed on their last legs. I have never been able to rescue daphnes from this stage. What you need is advice from vroomp (I think it was vroomp who told me how to plant daphnes).
After losing daphnes in pots, I decided to plant a pair in the ground. After losing them, I tired again. The second time I followed Walter Reeves's instructions when I planted one of them (see The Georgia Gardener's Guide for directions). That daphne is doing well. I planted the other one using vroomp's directions to create a mound with soil conditioner and plant the daphne in the mound. That one is also doing well, but not quite as well as the one planted using Walter Reeves's directions. However, this could be coincidence. You should know that the Walter Reeves method is backbreaking work. The other thing you must do is plant daphnes where water does not collect. The water must run away from the planting site.
If I were going to plant daphnes in pots again, I would probably fill the bottom half of the pot with soil conditioner and fill the top half with one part builders' sand to every two parts of potting soil and one part pebbles to every four parts of potting soil. I have no idea if this would work, but it's what I'd try.
Make sure you don't plant the daphne too deep - again vroomp is the source for how deep - I don't remember. And make sure mulch or soil or litter doesn't come up onto the trunk of the daphne. They're fussy little shrubs. As far as I can tell, they're also prone to viral infections, and you can lose them anyway to a virus. I haven't had to deal with a virus yet, so can't tell you much.

I have had two daphnes in pots for just about 5 years and I moved them from Marietta to Flowery Branch. They are in 16" pots with good quality potting soil and get full morning sun (east side of the house). I have some sacrifical moss as mulch to keep down evaporation and I water when the leaves start to droop (every 3-4 days). The pots have good drainage and soil retains water fairly well.

Thank you for the advice. I had read about planting them in the ground when I bought them, and thought it was a bit beyond me AND I wanted to have them where I could enjoy their fragrance, hence the pots.
I WILL try "mulching" them in the pots and see if that works.