True, I suppose he doesn't go all out with the barbarians are evulz theme, and he's definitely not as bad as most. But he does basically say that immigrant pressures resulted in the demise of the (western) Roman state, no? The implicit message is that immigrant management policies are necessary to ensure state stability, right?
He describes immigration as, in part the product of Roman power and wealth. Basically, that as long as one has an empire, one is going to have large-scale immigration, more into the empire than out of it. And he argues that unpredictable Roman policies, sometimes including trying to enslave or massacre immigrants, prompted people to choose armed immigration instead of unarmed immigration.
Now there are major problems with his specific arguments - for example, he doesn't seem to consider whether immigrant groups might have different land-use patterns than previously-present groups. Most of the known Roman settlements in Moesia Secunda and Scythia Minor are in the lowlands, and most of the known Gothic ones are in the highlands, and I think the same goes for early Slavic ones.
As to the state stability issue - I tend to think of states as
inherently unstable institutions, depending on violence from those in power against those out of power. So that affects how I interpret these topics.
The part of his understanding of migration that bugs me the most is his apparent presumption of a sort of hive mind on the part of the migratory group. The "Goths" were not merely a "people", but a coherent entity with consistent aims projected over decades. They had wagons, women, and children, ergo they were a whole mass of ethnically and politically well-organized humanity intent on settling in a new location. Which is pretty silly.
Actually, I don't see this in his text. I think identity could be more instrumental, and more flexible, than Heather does; in particular Heather doesn't leave much room for acculturation from subordinate groups into dominant ones; for example, Wulfila was not of Gothic descent but his parents had adopted enough of a Gothic identity to give him a Gothic name; I'm not sure whether the sacrifices mentioned in the Passion of Saint Saba [Sava] were only demanded of certain villages or of all villages, but it seems to imply that one [presumably Germanic] pagan religion was dominant within these villages, which, depending on how many villages were affected, may also imply acculturation. But Heather strongly emphasizes individual motivations, and regards the larger groupings as functional coalitions, not descent-groups. Also, I don't think the events of 376 [or 405+] can be used as a model for the events of 395+ or vice-versa. I think there are different kinds of events involved.