To investigate how the findings for the ideal small-molecule dimer translate to larger-scale systems with potential relevance for materials applications, we proceed by applying different GW -BSE-based diabatization techniques to a mixed donor-acceptor blend of rubrene and fullerene. Such a blend with low-donor content contains significantly larger molecules, exhibits substantial positional and orientational disorder, and allows therefore also a case study of the kinetics of the conversion from a photoexcited LE on rubrene to rubrene-fullerene CT states, typical intermediates for charge separation.