Yes you need more fat. My bologna is about 13% fat and hotdogs and sausages are 25 - 30% fat. I made some sausages before that were 13% such as my bologna is and they were dry too. I have a fat calculator in excel that I use to determine the mixture. Pork butt is about 25 - 30% fat and I add pork fat and venison makes up 50% of my sausage. I tweak the pork to get the fat content I want. Some want just venison and they you use 7# venison to 3# pork fat to make great sausages. My wife likes them cut more to reduce the wild taste. She's a corn feed meat person.
Johnsonville and other sausages in the store just have to be under 50% so they are probably in the 40 - 45% fat which is OK, but I like 30% for taste and healthy options. My turkey sausage was only 20% and was good, but it had a texture like spam or a processed meat. Not sure if it was the fat content or the Turkey, but it was still good. I noticed this also and several chefs covered it. The fat helps you taste the spices. If they are too dry you will not get the same flavors. Some of the sausage making sites guys vary from 20% all the way to 50% and its all personal taste, but I like 25 - 30% as a happy medium.
