Yep. Wrong motor.
Luxury GTs don't need horsepower. They need a perfect combination of torque and horsepower. Have you ever driven an RC-F? The car requires revs, because it's 389lbs ft of torque comes in at nearly 5000RPM. On a car weighing over 3800lbs, it wears thin. This isn't just my complaint, this has largely been a complaint of most critics out there. 0-60 times don't matter in a car like this. And I also fully expect this LC500 to weigh in close to 4000lbs, if not over, so torque issues could become even more apparent.
Luxury GTs need torquey motors. Not high revving motors where the ratio of torque to hp is way off. You want as close to 1:1 as possible for a car like this. Look at Mercedes, look at BMW, look at Jaguar, and look at Audi. They all have hp to tq ratios that are very close on their luxury coupes. Hell, even look at the Lexus LS460 itself, it uses a well balanced motor (albeit one that is VERY old and outdated), but it has torque that comes in early enough.
Again, as I said before, the 10-speed transmission will help with the lack of low-end torque, but I suspect much of the press will not be delighted with this motor in this car unless the gear ratios are absolutely spot on to mask these deficiencies.