The phrase "a host of duties" is correct and can be used in written English.
It usually means a large number or variety of tasks or responsibilities that need to be performed. Example: As the new manager, Emily was faced with a host of duties, including managing a team, creating budgets, and setting performance goals for her department.
Scientists on the ISS must perform a host of duties to maintain the full functionality of the station, but research will be their primary focus.
Freshmen have no leadership responsibilities, but have a host of duties to perform as they learn how to follow orders and operate in an environment of rigid rank structure, while seniors have significant leadership responsibilities and significantly more privileges that correspond to their rank.
They still run education and social services, and have a host of other duties, from street cleaning to planning controls.
Police officers have a host of other duties and lack training in asylum law or in conducting interviews with fearful and traumatized asylum seekers.
They were responsible for publishing announcements, performing land surveys, carrying out executions, and a host of other duties.
The 2010 reform legislation tasked the CFTC with a host of new duties, from regulating the derivatives market that almost broke AIG, to cracking down on oil speculation that drives up gas prices, to preventing conflicts of interest that encourage banks to undercut their own clients.
Meanwhile, the budget for the DWP ratepayer advocate is less than $2 million, and with a staff of four people, and a host of other watchdog duties, it only has time to investigate 50 or so of these complicated billing disputes annually.
The BFI, already lean, made around 35 employees redundant and took on a host of the Film Council's former funding duties and staff.
Out of necessity, pharaohs delegated most of their ritual duties to a host of priests, but most of the populace was excluded from direct participation in ceremonies and forbidden to enter a temple's most sacred areas.
The tariff's aim was to protect agriculture in the United States, but congressional representatives ultimately raised tariffs on a host of manufactured goods resulting in average duties as high as 53% on over a thousand various goods.
Cambodia falls under the Everything But Arms (EBA) tier of the EU's Generalised Scheme of Preferences (GSP), which means that it – like other least-developed countries – can export sugar and a host of other products to the EU duty free.
