Hello @Mark_MacBeth,
one option could be multi-homing tasks in one project to then have a total overview.
Or you can set up graphs to give you a total number of all projects you want (you can enable filters also)
A while ago I listed some ideas here that might help.
And see more info on number custom field chart here Using charts on project dashboards to track progress | Product guide • Asana Product Guide
Workload can surely be helpful also in your case.
For further in depth reporting capabilities you can look at Bridge24 for example.