Mark, you seem to be taking an overly negative attitude when discussing these things. It seems to be clouding your objectivity, especially when someone dares to disagree with the pronouncements of St. Zubrin.

There are some things that you're neglecting to consider as well. For example, are you thinking the mission will go directly from an interplanetary trajectory to touchdown (like Mars Pathfinder and MER) or will it enter orbit around Mars (like Viking) first? Proceding directly to the surface can work but it's a lot more risky than entering orbit first, then descending to the surface.

If you enter orbit first, you have two choices. You can A) burn thrusters to enter orbit, consuming a good amount of propellant, or you can B) try aerocapture, an as-yet untried technique.

Would your vehicle leave the equivalent of a Command Module in orbit around Mars, or would it carry everything to the surface? If you carry everything to the surface, then you're carrying tons of dead weight into the Mars gravity well, stuff like the heat shield needed for return back to Earth, food only needed during transit, etc. That makes the lander much heavier than it needs to be, greatly increasing the amount of propellant needed for landing and for takeoff. Remember, weight is the enemy. Back in the 1960s, NASA literally spend millions of dollars to save a few pounds on the LMs. Weight was literally that critical.

If you decide to leave that stuff in orbit around Mars, then your lander can be much lighter. That was one of the biggest driving factors for why Apollo went with the Lunar Orbit Rendevous technique. Now, how much propellant would you need to slow both the orbiter and the lander down enough to enter orbit around Mars? The lander is going to have to be a substancial vehicle, far heavier than the Apollo Lunar Modules (as discussed below in my reply to your Cassini post). How much propellant would it take to put that lander into orbit first as opposed to not being able to produce the fuel needed for the return flight from local materials? Also, what happens if you get to Mars and can't land for some reason, such as equipment failure? Do you doom the crew to death, or do you plan the mission so they have enough propellant to return without landing? If you have enough propellant to return without landing, then all you gain from production of the propellant from local sources is the fuel needed for liftoff from the surface for return back to orbit. This can be a considerable savings, but it probably doesn't change the amount of fuel needed for the return trip back to Earth very much.

Once you're in orbit around Mars, it takes very little propellant to go to Phobos. You'll probably have the propellant needed for the return trip anyway to allow for emergenices, so landing to get propellant for the return flight isn't an issue. A first trip to Mars orbit only could be seen in the context of Apollo 8, a good test for systems, navigation, communications, and the crew. Once in orbit, the crew could do useful things like deploy navigation and communications satellites. Once at Phobos, the crew could exercise near real time control over rovers and landers.