They will work great once you get to Phoenix.
Actually, they will work quite well. I had issues in our last coach, an Allegro Bus because the BTUs and CFM weren't high enough and the defroster vents weren't adequate to get what air did come out of the vents to the windshield. It always fogged in the corners and you couldn't see the mirrors. The Bus did have the overhead "trucker's" fans and we used them all the time to try to circulate air but the result was limited. WE also froze out feet from lack of heat and poor firewall insulation. On top of that there was no split setting on the heater control. You wither got all floor heat or all defroster but no half and half mix.
Driving our Entegra in winter is a dream compared to the Tiffin. There's more BTU in this heater/defroster and it moves more air volume (CFM). They also have the defroster vents located to actually wipe the entire windshield with airflow so I can still see my mirrors. And the superior firewall insulation means my feet don't freeze and the dash control even allows me to split the airflow between the defroster and floor heat vents. I'm very happy with this system and originally thought I would have to add the overhead trucker's fans but now I find I don't need to do that.
FWIW - I was impressed with the heating system in the American Eagle. They use a system with separate heat exchangers and blower fans for defroster and heater. It's a system like used in fire trucks and they will roast you right out of the cab if you crank them up.