Most of the mass (fuel) will be waiting in orbit. They need to bring down to the surface only the fuel to get back to orbit so they won't need half of a Saturn V. They still need to launch a lot of fuel from Earth.
I wasn't thinking about the whole journey back home, just the first part of it which looks damn hard to me: how do you get a space craft away from Mars? You need to reach escape velocity, and that's 5 km/s (> 11000 mph).
You'll have to build a complete launch site for that.
OK, got that. Did some further reading (again) on the topic and it's still about 4 km/s to reach the orbit. People are working on it, but for what I read it looks hard to overcome for 2030...
The Design Reference Mission calls for generating the fuel on the Martian surface, so you only need to drop a small amount of hydrogen feedstock to make the rest.
You need a huge launchpad to launch a 100 ton vehicle. You don't need it for something weighing only a few tons.