'responsible for assisting' is a perfectly correct and usable phrase in written English.
You could use this phrase when referring to someone's assigned duties, such as in the sentence, "The manager is responsible for assisting customers with any questions or inquiries they have."
ISP is responsible for assisting member countries in preparing investment projects for domestic financing and formulating technical assistance projects.
In Afghanistan, a senior U.N. diplomat is responsible for assisting the transition to a fully elected government.
For each task, a lead was assigned and the other person would be responsible for assisting the lead.
The University Tax Department is responsible for assisting in the determination of an individual's residency status for tax purposes.
She was responsible for assisting the routing editor for East Asia, South East Asia, Australia and the Pacific region.
The United Nations is responsible for assisting and supporting the election process under Resolution 1770, which was approved by the Security Council in 2004 and renewed last August.
"We are stretched almost to the limit," said Francine Dupuis, the spokeswoman for the Quebec government agency responsible for assisting new arrivals.
Mr. Adoboli worked for the so-called Delta One desk at UBS, responsible for assisting clients dealing in derivatives based on exchange-traded funds.
Australian investigators are only responsible for assisting search efforts for MH370, while the Malaysian government is working to establish why the plane disappeared.
Departments are also responsible for assisting the Controller's Office in completing the biennial physical inventory of the University's Moveable Equipment Inventory.
If a data loss incident occurs, you and your department will be responsible for assisting with identifying and communicating to all affected parties.
