I also had a 2010 FD3. When I bought it it's hybrid battery level was 14% when I checked it from Stafford. Because of this I could buy it for way cheaper than the regular price of a car with good battery. And I used it for 3 years without replacing the battery. Mostly I've driven it around Colombo (actually short distances 10km round trip everyday to office and back). However when I visited my home (upcountry) I remember 2 or 3 incidents when I had to completely stop the car to open the gate at my home entrance which is an extremely steep private road. And still were able to move up normally, however if I had to stop twice like this on this steep road, car would move very slowly uphill (with full throttle) due to lack of support from battery. This is the only issue I had during those 3 years.
However even after 3 years, I never replaced the battery. And I put on an advertisement to sell the car. Just like you've told, I could've sold it in 2 days but I also didn't want to sell it without explaining full picture. I explained the battery issue to every single person who came to buy it. Most of them didn't want that trouble and went away. If I hadn't have told this, or reduced my price I could've easily sold it. I didn't want to be fraudulent. To every single buyer who came to see the car, I explained the battery issue and the amount it would cost for them to fix a new battery. And still my price wasn't that cheap either, so it took some time to sell. I managed to sell the car for little less than the market value at that time, but I sold it for 9 lakh more than what I bought it for. Used 3 years, didn't replace battery, explained the buyer that they have to replace battery soon if they are buying it , and still managed to keep a 9 lakh profit. It's been like 2 years since I sold this car now. About an year ago when I called him, he was still using the car with the same battery.
My advice is, if you can buy another car with similar options for this price (which I seriously doubt) go for it! , don't buy the FD3. You don't want all hybrid trouble. But if you can find an FD3 with a decent battery ( 20% or more) for a cheaper price you can try this car. Probably you can buy FD3s for the same price they sell 20 years old ES1 models.