8 cabin crew on the A330-300 deal with average of 40 passengers.
4 cabin crew on the B757-200 deal with average of 43 passengers.
Flights won't have 100% LF all the time. All EI flights have min crew on aircraft and service levels don't suffer. This is a non issue and as usual unions don't want staff to actually do a decent days work.
It will only be a matter of time before US carriers are forced to cut costs and become more efficient if they want to remain viable between US and Europe. Fuel, airport charges and Government taxes are only going one way and passenger income is in most cases going the other and the gap will have to be reduced at some point.
For all the extra CC on some US carriers, service levels leave a lot to be desired.