Are you paying your current IT team to do proactive monitoring and documentation or do you instead pay them on a time/materials basis when a problem arises? If T&M, there may be a disincentive for them to fix the problems so they don't resurface.
with a more complex, unstable setup like this, a couple basics should be in place before I would hire another person. Ensure your IT group has:
1. Developed detailed, written documentation of your physical and logical IT architecture. This means documenting the existing hardware configurations as well as documenting software and OS configurations, key data flows and backup procedures. Everything from servers, network switches, and the clients.
2. Documented incidents each time and regularly reviewed the data for trends. Documenting these incidents includes noting who is having problem, which location and piece of hardware, capturing problem description, & documenting root cause once fixed.
This is the bare minimum to expect from your current IT service provider. When you have this documentation and the problem history, then a new or existing IT support person can start to pinpoint mis-configured or bottleneck components of architecture. It also prepares you for changing IT service providers if this becomes necessary.
