What challenges do you think came with governing an empire as large and diverse as rome?

The challenges of governing an empire as large as Rome's and with the various ethnic groups contained in it were many. The main challenge was communication. Although the roads were Excellent, it still took time for a communication/order/letter to reach the far corners of the empire. The distances also affected things such as tax gathering and rescue operations. For example, when there was an earthquake in Antioch, it took a considerable length of time for even the emperor's orders for the military to help the people to arrive, not to mention the physical aid in the form of rescue equipment, medicines and other humanitarian help.