Hordes are great, but not unkillable. I had an encounter with the Vandals at the end of my Saxon game, just as I was finishing my conquest of Spain and preparing to invade Britain. They came through by Massila after ransacking all the Italian pennisula cities for years(all the cities down there are rebel and low pop now). They broke off one stack and sent it to Massila, which my garrison force was able to beat. Then the rest of them headed up north to my capitol.

I had three consecutive sieges, first killing 3300, then around 700, and finally I broke the last siege myself. By this time they were mainly down to Warlords and Steppe Horde Cavalry(all their infantry except for like 100 had died trying to take their city). I isolated their remaining stacks and thanks to all the Saxon Sea Raiders I had gathered for the occasion was able to take out the last of their forces including their commander(who was oddly named Gogodolus(sp?) the Good, a kind benevolent Vandal faction leader who spent his time terrorizing the civilized world).

They came awfully close to actually taking the city on the first siege, I had three or four units fight to the death on the walls. Those Steepe Chosen Horde Warriors are tough to beat back. I thought fighting and defeating the horde was a nice touch to the end of my game, like proving my strength to the rest of the world. Now I think i'll try a horde faction and see how I like sacking the world.