Defences of the western Roman empire in 5th century

[Theodosius the Great]

Vortigern,

to the people of the 5th c., nothing changed, it was the same as the other warring emperors of the 4th c., only now they were warring generals - big deal.

How can you say 'big deal' ? Some North African provinces suffered much more heavily than others. The country side was devastated. And you've said that North Africa never fully recovered from the Vandal conquest (on another thread)

For the population in the path of their armies, there sure was no difference between the armies of Constantine the Great or those of Gaiseric.

Again, how can a civil war compare to invading barbarians bent on conquest ? In civil war, Romans armies, afaik, did not scorch the country side. From the locals' point of view, being taken over by barbarians must have been a much more brutal business, I would think.
(Good point, btw, on Arians vs Catholics)

For the taxpayers, a general like Gaiseric could mean a tax relief.

The benefits of any tax relief would be more than balanced by the devastation to the land, though. The locals' fortunes were better off under direct Roman rule and higher taxes, IMO.

And when Gaiseric stopped paying taxes to Rome or halting the shipping of food to Italy, he just acted like generals and usurpers before him.

Yes, but it must be said that he attained a level of unprecedented power and influence because of his unassailable position in North Africa. Gaiseric was the most successful warlord after only Attila, IMO.

~Theo