Your results are normal and OK. The beauty of mulch is that the soil never gets wet which would cause root rot, but never gets dry. The beauty of mulch is that it keeps the root zone cool in summer, protects them in winter, it keeps weed from invading the shallow root zone of rhododendrons and azaleas, as well as conserving water. A typical mulch layers is a 2-3 inch layer of an airy organic material such as shredded leaves, leaf mold, pine needles, or pine bark mulch. Many growers find that the roots tend to grow in or near the mulch.