propagation challenges

In propagation by cuttings, there are so many factors to consider. A month or so ago, I took cuttings of Salvia officinalis var. minimus. Some of the cuttings I struck in perlite, a few more I struck in potting mix. Two weeks later, roots were snaking out of the drainage holes. So easy, I thought. But when I unpotted them, only a couple of the cuttings in perlite were just barely putting out roots, the ones in the potting mix had well-developed roots. I figured I learned that the cuttings were easy in potting mix, and slow in perlite. I took more cuttings, struck them in potting mix. They all rotted. I tried again two weeks ago, striking the cuttings in Pro-Mix. Two weeks later, still no roots. So either I did something different when I took the cuttings (did I take a heel the first time, or did I not? Did I take tip cuttings or basal cuttings?), or it is timing, both, or neither. The heel cuttings that I took of lavender at the same time are looking pretty bad, and the rosemary cuttings look okay (no roots yet though). Incidentally, the cutting I took of the rose 'Bolero' at the same time, is growing roots out the bottom of the pot. Go figure.