Thats why GS has GS300h variant in Europe .For comparison purposes, the current GS450h, a much smaller and lighter car than the S300 hybrid, is rated at 45.6mpg (UK gallons) and 145.6 g/km CO emission, which is still way too thirsty and tax-expensive for most Europeans. Lexus still has lots of engine downsizing to do if they're to catch up to the demands of the rest of the world.
And GS450h actually does really great against 3.0 diesels when it comes to emissions, this new version will do crazy good if it comes down from LC500h.
Lexus, like everyone else, should offer different variations of their engines, and let the buyers decide. This is what they have started with new 2.0t and 300h and should continue with 500h, 250h and others. There is no one formula that fits every market.
Europeans are all about NX, RX and future UX, talking about LS makes little sense... it has and will always have miniscule sales in Europe. IS is in better shape and GS will never be selling great unless they sell at big fleet discounts which is how people buy A6 and 5 series.
New NX and RX is where Lexus has to go in Europe and UX should also be a great step forward.