Logic 9.1.2 now displays both the average activity on all audio threads it is processing, and the activity level of the highest peaking thread. Here is a sample image showing the new meter:

The gray bar shows the current level for the most active thread. The small yellow line shows the average activity level for all currently active audio threads.

You may view a discrete breakdown of all the activity for each thread by opening the expanded System Performance window (accessible by double-clicking the meter on the Transport, or selecting Options > Audio > System Performance from the main menu).