A prime example of why HLLVs are needed.
Dateline 2018
After failing for three straight days to launch the second segment of the first manned lunar mission in 46 years, the entire mission has had to be canceled. Seems too much of the propellent in the first stage, already in orbit, has been lost due to the delays facing the launch of the Atlas V/Delta IV after an undetermined problem was discovered with a fuel sensor.
As long as rockets remain the unpredictable primitive beasts that they are, multi-launch missions will be far less reliable and successful than single launch missions. HLLVs are the only way to go.