Having a representative represent you is not required in the immigration process as the Canadian government treats all applications the same.
Hiring a representative would make things a lot easier for you.
As he or she must be authorized by the Canadian Government, the representative will take responsibility during the immigration process.
The correct procedures and forms will be followed as the consultant representing you, would not want to be sued against.
The job of the representative begins at the very beginning, which is filing the application to representing you to the Canadian government.
A representative would also ensure that there are zero errors in the application.