I've played the scenario about a dozen times in the past couple of weeks, first as the Ostrogoths, then as the Franks, and finally as the Anglo-Saxons. Holy crap, this is a hard scenario! My best results so far have been as the Franks, and I suspect that's because the Franks aren't as hemmed in by other barbarians as the Ostrogoths and Anglo-Saxons. Both of the latter have gotten bumrushed by other, AI-operated barbarians and knocked out before they could turn on either the Byzantines or the West Romans and take them down. I think what's going on here is that the habits developed from playing regular Civ3 are betraying me, because while building a high culture score is still good in terms of final victory, it takes resources that could be better spent building bigger armies to trash one's neighbors, including the decadent Romans. On the gripping hand, if you don't build things like temples and aqueducts, the barbarian towns start getting too big and either prone to plague or periodic rioting...and the only way to relieve the population is to either build a seemingly endless stream of migrants or workers. The migrants either wind up building new & vulnerable cities on the periphery of your kingdom, or just shift the population around, neither of which is a very good solution. Workers pose a similar problem - after a while, they've chopped down all the trees and built all the mines, roads and irrigation ditches they possibly can, and then they become targets for other barbarians.
On the other hand, the Huns never seem to get very far towards Rome themselves. I dunno. I'll keep plugging away at this for a while, but I'm open to suggestions...should I be whacking on my neighbors the Vandals and Franks? Should I be pursuing more aggressive diplomacy?