Cumin, or comino, as it is called in Texas, TexMex or Mexican cooking, it a very powerful spice. Use it right, and it adds a distinct, but subtle and pleasing flavor to food. Use too much, and it will easily ruin an otherwise good cook. I rarely use comino in a rub -- unless I am doing a TexMex or Mexican dish. It wouldn't occur to me to use comino in Carolina BBQ, but I live in Texas.
You really can't go by a recipe when comino is involved. You really have to add small amounts at a time, until you have just the right amount. Add, taste, add, taste, and stop when it is right. The line between just enough and too much is pretty thin.
If you do add too much comino, you can sometimes save your food with some nutmeg. Nutmeg can balance out too much comino, within reason. I've used it to save a pot of chile that I overloaded with comino.
You need to taste your rubs before you put them on the meat. Wet your little finger, dip it in the rub, and taste it. If you taste something offensive, fix it before you use it.