If one master is responsible for targeting too many endpoints, the injection rate might become a limiting factor. To fix this issue, you can split traffic at the master. By splitting transactions and moving those transactions to a different master, the injection rate is less likely to become a bottleneck.
An alternate approach is to add more masters into the system and divide the total work more equitably across the masters. The level of effort required to redesign using this approach can be high but might be required to improve NoC performance.