"vast responsibility" is a correct and usable phrase in written English.
It is typically used to describe a significant or large amount of responsibility that someone has. Example: As the newly appointed CEO of the company, John felt the weight of the vast responsibility placed on his shoulders to lead the company to success.
It's also a vast responsibility.
"The Italian state owns way too much heritage; with owning heritage comes vast responsibility.
You have to wonder about giving a position of vast responsibility to someone who can beat Mr. Gonzales in dishonesty.
In 1947, George C. Marshall, then the secretary of state, challenged Americans to "face up to the vast responsibility which history has clearly placed upon our country".
Halliburton's former subsidiary, KBR, which was once run by former Vice President Dick Cheney, has won contracts worth more than $24 billion since the start of the war, giving it vast responsibility for reinvigorating Iraq's oil sector.
Sometimes he feels vast responsibilities as a home-care worker: he once cared for New York's archbishop, Cardinal John O'Connor, when he was dying.
After eight years as secretary of health and human services, Donna E. Shalala has a little advice for the Republicans who will soon replace her and thereby inherit vast responsibilities for the nation's health and welfare.
Energy officials and outside experts agree that the department has serious problems, with roots in the vast responsibilities and liabilities incurred during the cold war in making 70,000 nuclear arms.
But behind the scenes, some participants say, Mr. Negroponte and General Hayden have been consulting with lawmakers and military and intelligence officials in an effort to flesh out their new roles, under a law that has assigned them vast responsibilities but only limited powers.
"Google is a large company with vast responsibilities, and those responsibilities are only likely to grow.
As Lord President he assumed vast responsibilities over domestic issues and chaired the War Cabinet during Churchill's many absences.
