I have the very same problem with Carefree Wonder. It looked great the first year and has been going downhill steadily since then. I was going to replace it, but after hearing that you've had the same problem, I may just decide to live without it.
Carefree Delight, on the other hand, improves with each year. It didn't impress me that much at first, but now it's vigorous and large and blooms like crazy.
