Well, I am going to have to agree with a lot of what he says. A beehive oven is the simplest to build with mud or mud brick. Next would be the Pompeian style oven with brick, then a low-dome type or barrel oven, with a square oven not practical with standard masonry units alone.
When heat is discussed in relationship to the dome "focusing" it, it just applies to active heating elements. Radiant heat is disseminated in all directions equally for equal differentials of thermal conductivity. No matter what shape oven you have, if the thermal mass is all heated to the same temperature, there are no hot or cool spots, either in the mass or in the radiant energy available at any given unobstructed point inside the typical personal oven (assuming no opening for a door).
So, the main point is to build whatever type you like, then insulate the crap out of it, under and over, and learn the firing and cooking regime that works for your particular oven.