I have had the same problem at shops in my local area. I actually watch what the service advisor writes on the work order and have had to correct what he wrote because he didn't write down the explicit instructions of what I want done.
Giving explicit instructions didn't help. The local shops still didn't do everything I requested.
I think the mechanics are given a time frame to complete a vehicle whether it's done correctly or not. My guess is if they actually took the time to complete the job and repair everything correctly, they would probably be accused of working to slowly and eventually lose their job.
I finally located a Coach-Care facility 180 miles from where I live in Spokane, WA. I have used them a few times, and the repairs and service has been excellent. They have qualified mechanics that know the chassis, engine, trans, and all related coach equipment, and have completed everything exactly as I have requested.
I don't know how much extra training and experience the mechanics and service advisors have to go through to be a certified Coach-Care facility, but I will drive the 180 miles to have work done there because I know it will be done right.
I just wish there were more of these facilities across the US.