Look does have a default shallow seatpost angle, but, turning it over (also in my case), you go to 79 degrees anyway. I have fairly long forearms, which dictates that for a low / flat back position I need either to have a very short headtube or somehow compensate for it with a low stem position (which the Look allows doing). My current position is as low as it gets (no wind tunnel testing unless I go somewhere abroad... not an option), I can play a little with stem lengths / aerobar positioning, but that's it.
While disc certainly would give some extra speed, I wouldn't believe it is as big as more than 2 kph, so I still seem to have the most un-aero TT bike around
Another explanation might be the powermeter gives wrong readings, but in this case, I'm tempted to believe the watts since I have a Quarq on my roadbike to compare to, and also ran a Powertap a year ago, and all these have shown more or less similar readings (no sudden "gains" or "losses" in fitness, as much as I have it at all).
Hmm i have a few ideas but a head on shot (even on the turbo) would answer a few of my questions, a lot of drag is defined by the bits that hit the air first!
If the position is more aero I'm sure you could adapt to it over a few months of consistent riding in the position. I always do my winter turbo sessions on the TT bike so that I never lose the flexibility and comfort I have on it. If i'm being honest the hip angle looks like it might restrict power a bit, but i would only raise the stem by 5-10mm. Its amazing how little changes can help. The difference with a disc would only get another 5-8W back over an 808. Maybe use a buff or similar, to control the hair flapping in breeze outside of your helmet, or cut it if that is your preference.
By the way the power graph looks nice, could be a little tighter but I know that's very hard to do.