Riff-raff units too strong?

[Titus Marcellus Scato]

What the Numidian and other North African units lack in armour protection, they make up for with high defence skill and high quality weapons. They aren't riff-raff, they are good units. There's a reason why historically Carthage only managed to conquer the coastline of North Africa and not the interior.

Also, cavalry in EB, even heavy cavalry, is not the nigh-invincible steamroller it was in the stock 'vanilla' R:TW. They aren't like medieval knights (except for the some of the cataphract-like units). So don't expect cavalry in EB to have the same capability as in vanilla - cavalry has been made more historically accurate (i.e. weaker.) Cavalry need to make the enemy rout to kill them in large numbers, and that usually means hitting the enemy from two or even three sides simultaneously, and having a local superiority in numbers at the point of contact.

EB is set during the pre-Christian era, when infantry was the dominant force on the battlefield, not cavalry. (Except for the north-eastern steppe and Parthia, which is horse archer territory). Except for those areas, you will achieve much better results with a combined-arms force, not an all-cavalry force. As Shadowalker says, that's the real key to EB, combined arms, using different unit types together, and finding the right ratios to have between them. And the backbone of most successful armies, for most factions, will be infantry. Cavalry's role is to support the infantry, not vice versa as in the medieval period. The only time you should have an all-cavalry army is when the enemy have nothing except cavalry too.

As for storming cities, that's definitely an infantry job. Cavalry are weak in street fighting.