Welcome to flyertalk.
I have never been to DOHA but I have tickets thru there in May. I had the same question and have read many posts in the Qatar forum. You will find DOHA has a website that explains it services for mobility challenged.
I have similar issues, as does my wife. First, I always have a note in my reservation for wheelchair assistance. Often this is provided as you leave the door (you can request from your seat of the plane. I am not familiar with this). I would not wait to get off. Most airports have long walks, this one seems to be no exception. According to my research on FT, DOHA recently added one or two concourses. Also, there is security to flow thru, perhaps 2. Also, there are some flights that require busing, and lines. If you don't get a useful response, call your airline, review other forums associated with your airline in DOHA. While those on FT likely will tell you over an hour is not a problem, preparation is the key.

I hope you get some more direct help from someone else more informed. We are doing DFW-DOHA-CPT