Maybe you are trying to over "tech" things. My Mother-in-Law is an incredible quilter and many quilts were made by tracing around a cardboard template and cutting with a pair of scissors. Sometimes, we forget that rotary cutting isn't for everyone or every occasion.
You might be having a problem with your sewing machine feeding your fabric unevenly. Have you been starching the pieces before cutting and press after each seam? Squaring up blocks is very important as well. My really important tools are a good square and an iron. I can live without a rotory cutter (I'm sure someone just fell off their chair when they read that). A bamboo skewer, awl, stiletto (or something like that) can help a lot as you feed your fabric. You might not be sewing a consistent seam (1/4 inch is what most patterns call for).
I hope these ideas help.