I have had some different experiences. For example a group that goes to 18" @ 60 might not be the fault of the broadhead, but rather the vane. You can take the approach of selling them different broadheads, or vanes that have enough drag for the broadheads they want to shoot. I guess most shops just take the route of telling them to use a mechanical.
I have spent a fair amount of time tuning thru a shooting machine. That takes the human element out, but increases the time it takes. Not everything is set in stone and changing one thing can change multiple things. I also always make sure results are repeatable, so it's a matter of the same thing happening in a follow up group, that takes time as well. I'm not saying this is something that is going to take all day, but yes, sometimes it is a couple hours, especially while working with someone on it.
I do my broadhead tuning at 65 yards, that takes a while just walking back and forth. When you use a shooting machine you need to do it on each arrow. It's faster for me to just shoot it, but many times when I'm playing with something really testing it I'll put it in the machine to remove the loose screw element.