Gaesatae are so not overpowered,Hammer and Anvil, skirmishers and Viagra are great tactics to take care of them, when I was playing my Medium battle difficulty(like you should) Those Gaesatae (in those north italy rebel provinces) were easy Imho, sure if you stick like 20 of them there gonna wtfbbqpwn you but thats why they call them elite units.