if I remember correctly when you look at the ECAM electrics page you can see it as a percentage figure beside the generator symbol. If one of them says 90% and the other one says 10% then you 'might have' a problem....
Given that the system is non paralleled, % generator loading would seem to me to be irrelevant to this discussion.
I suspect the mechanical constant speeding function of the IDG is at fault. It may be a simple as low oil quantity causing the problem. ( exacerbated by the change in attitude ? )