DOH has only 10 gates (atleast till last year) & its very easy to connect. they bus their pax to the terminal on arrival, you go through security - which doesnt take long & then you are in the departure area & back to the bus for boarding.
the last time i was there it was very crowded with people on the floor.
you can go to oryx lounge & pay straight on arrival there. the impression i had from their website was that you had to prebook the lounge. but thats only if you are booking their meet & greet service - Al Maha.
my mom loves DOH when shes flying alone as she doesnt have to worry about short connection times or long walks till the gate or being in the wrong terminal.