I think that this year's smaller's diffusers have forced teams to create a sort of Tri-plane rear end. Bear with me for a second, I think that the rear of the car uses the diffuser as a diffuser for the floor and as a third wing. You have the main wing on top, you have the beam wing in the middle, and the diffuser/wing on the bottom. Think about it, the regulations this year were worded in such a way as to separate the flows in the rear of the diffuser and wings. So the best team is the one that improves the efficiency in these three areas. That's one of the reasons why the RB7 currently features a smaller rear wing than other teams.
Another thing that catches my attention is the ducting for the RB7, if the drawings from Scarbs are accurate, then what is happening is some hot air from the cooling system exits over part of the sidepods, the rest gets squeezed into a cavity that travels upward, into a diffuser(like one on a trumpet or an a/c vent) which then exits out over the beam wing. Basically all the hot air from the cooling system exits out by the beam wing of the car, slightly lower than this hot plume of air, is the exits for the exhausts, and diffuser. In essence you end up with a lot of relatively cooler higher pressure air, surrounding a lower pressure hot air center.
By moving as much relatively cool air out of the way with the front end, you in essence increase the pressure on the front end of the car, and decrease it on the rear end as the by-product of cooling. If that is what they are trying to acheive, then it would make more sense to try to trap that hot air center with the rear body work than it would be to try to put the diffuser as low to the ground as possible. Not that those are your only options, but just an observation.
The height of cultivation is really nothing special. It is merely simplicity; the ability to express the utmost with the minimum. Mr.Lee