I completely agree with Donald.
I remember a similar situation in one of my previous projects where I was a team member. Like you mentioned, there used to be a lot of "fire fighting activities" and some "ad hoc" requests from the clients on a daily basis.
What my manager did was acting as a "Firewall", if you will, between the clients and our team. This really enabled the team members to perform well in their day-to-day activities. Also, we made tremendous efforts in fixing either the process or systems or both to provide a stable environment for the users to work with the systems. This eliminated the "fire fighting activities" a lot.
HTMS(Hope this makes sense).
Magesh.