I'm sorry to hear of Lexus hybrid owners' disappointment. One variable that I didn't see mentioned in this thread is TIRE PRESSURE!
Check you tires every time you fill up. You'll be surprised how often they need topping-up. Keeping the tires inflated 2-4 psi over the recommended pressure will significantly improve mileage. I imagine this will be more so in the Lexus, with its larger tires, vs my Civic Hybrid.
My understanding is that the Lexus is designed for performance, not mileage, so it may take time to learn to drive it most efficiently.
Good luck!