8 days post op FUE, afraid areas were over harvested. Opinion? (photos)

In my opinion you will have to wait for the rest of the donor to grow out some more. Like 1-2 months. However it does not appear to over harvested. 

Your donor area will always look "thinner" proportionate to the number of hairs taken out after a FUE harvesting surgery.  The hairs will NOT grow back from the donor area (where it was taken). If it all goes to plan the donor hairs will grow in the area it was transplanted.If you are having issues after your surgery, the best person to ask is your surgeon who knows the specifics of your surgery.

It is too soon to tell. You must wait a minimum of 3 months post-op to see growth. Use minoxidil 5% nightly and be patient.

Looking at your photos, more that overharvesting one questions the location of the harvesting particularly with the grafts removed from the upper neck.  These are likely outside the permanent zone. 

I understand you had 3000 grafts harvested in a single session. In reviewing the pictures I can see that the harvesting was confined to the back of your head and sides behind the ears. I also can see that they went very high toward your crown and very low onto your neck. Given the surface area of excisions I think they took 25- 30 grafts per square centimeter, which is an aggressive harvest. The grafts taken low and high may be affected by further balding -  I hope they told you this. You describe your self as having low density to begin with, so it is possible that they took almost half of the hair you had in this area. If they used small diameter punches and did not have a high transection rate, it is possible that the donor area will still look OK over time; if not, it will look sparse. Then there is the question of will all the grafts survive. It is going to take about 8 to 10 months for you to see the final result. Good news is that it seems to be healing well, so lets hope for the best. Good Luck.