This short wheel base car is in need of more floor area. That's cheap downforce. Too bad they can't do anything about it now, unless they put a 100mm spacer flange between gearbox and engine.
I agree that the mid body and rear are questionable designs.
Though we may need some driver quotes to verify what the real issue is.
the car may well feel pretty good and balanced, without drs activation, but it just lacks total downforce.
When that is the case, then it's probably fine details as marcush suggested.
If it doesn't feel balance, when drs is not in use, then we can say there definitely is a problem with the front or rear.
The DRS and KERS is a compounded issue.
I was lambasting them last year for their low nose and bulky saftey cell; and it's good that they changed to a high nose and high cell, but the shape has to be questioned.
that kink under the nose looks suspicious. I'm not sure what it is doing, but it looks like the regulated nose area has to do with how they shaped it.
According to how the bottom of their safety cell naturally curves, the bottom of the nose would have been much lower. However they forced the nose to be close to the 550mm limit mark. This resulted in a higher degree curve that may not be taken too well by the air flow.
This looks to be affecting splitter down-force and side flow as well.
The car doesn't have many problems, i think, it just has a small amount of deep rooted problems. Luckily they seem repairable.