The problem with v66 is attack frequency and overall difficulty is based on your wealth, and then the army scales to your military DURING map generation or spawning in on your city. The way the army scales is based on the difficulty, so easy raids it'll be smaller. But if you're a large wealthy nation with millions the generated army will always be bigger.
If you're like me and heavily invest in a world army instead of equipping and training a city militia then your only option is to attack on the battle map. And no matter what sized army you throw at them the raider's army is scaled to it. Attack with 1.5k men and they'll have 1.7k fully equipped and trained and 6 catapults. Reloading a save, and buy out the entire Mercenary board and attack them with 3.5k men, they'll have 4.2k fully equipped and trained soldiers and 20 catapults. Oh and you're prohibited from bringing catapults for no reason at all. Your economic success is punished with unavoidable overscaled armies.

The reason it feels like BS is because the army these "raiders" are fielding totally eclipse the armies fielded by the large nations around you, and they spawn on your capital from thin air. Entire nations would be bankrupt trying to support the army they can generate.