I have used a Harmony for our home theater area where I only have a Joey connected to the main Hopper. My Harmony 650 has been working for over 2 years fine. The thing is you really don't have to set the code as a Joey. You use the code for the Hopper. Posted about this a few times, but here is a shortened version that may get you going. If I remember correctly, if you use the wrong Hopper code the power off will not work. Since it's not really a power off command that needs to get sent, but rather a power toggle. I may have had to monkey with the Harmony software to fine tune the commands so if this does not help then post again and I can try to help.
What I ultimately did is in the MyHarmony interface for the Hopper w/Sling I used:
Dish Network (for the manufacturer) HPRSLNG (for the Model Number)
That got my red button to FINALLY work. At first I thought it was a bad button as the other colors worked. As a work around if you still have the red button issue is to modify the top 4 selections on the LCD panel itself. Make one of the 4 settings on the first page set to "Red Button". May have to set it then drag it from page 5 to page 1 in the Harmony interface. But when I first could not get the red button to work this seemed to solve it. But chose HPRSLNG and the red button works fine.
If you have a regular Hopper, use: HPR2000 (for the Model Number)
Try not to use just "HOPPER" when setting up the device.
I've been using the harmony for awhile but have been frustrated by two things. When I switch from input 2 of my TV which is for my Roku to Input 1 for my Joey it does switch inputs. The problem is when my Joey is turned on the display is of the Tv shows the "Search screen" of the Joey instead of the channel selected. Secondly the Harmony will turn on the Joey but in the "Watch TV" function of the Harmony. But the Joey won't turn off using the Harmony should I switch back to the Roku. Inputs do switch.. Secondly the Harmony will turn off the Joey If I switch the Harmony to only control the Joey and use the "Power Toggle" button. When I set up the Harmony I told it that I was using a Dish network Joey. My other Harmony remote is setup to control the 1st generation Hopper and it does turn the tv off. Video selection is ok for that set uses a Home theater Receiver.