  If low-energy SUSY exists, LHC data favors a high mass scale for scalar
superpartners (above a TeV), while sfermions and the dark matter can be
parametrically lighter -- leading to a so-called split-spectrum. When combining
this fact with the motivation from fundamental theory for shift-symmetric
scalars (moduli) prior to SUSY breaking, this leads to a non-thermal history
for the early universe. Such a history implies different expectations for the
microscopic properties of dark matter, as well as the possibility of dark
radiation and a cosmic axion background. In this paper we examine how
correlated and mixed isocurvature perturbations are generated in such models,
as well as the connection to dark radiation. WMAP constraints on multiple
correlated isocurvature modes allow up to half of the primordial perturbations
to be isocurvature, contrary to the case of a single isocurvature mode where
perturbations must be dominantly adiabatic. However, such bounds are strongly
prior dependent, and have not been investigated with the latest Planck data. In
this paper we use the example of a SUSY non-thermal history to establish
theoretical priors on cosmological parameters. Of particular interest, we find
that priors on dark radiation are degenerate with those on the total amount of
isocurvature -- they are inversely correlated. Dark radiation is tightly
constrained in the early universe and has been used recently to place stringent
constraints on string-based approaches to beyond the standard model. Our
results suggest such constraints can require more input from theory. Data from
cosmological probes -- such as Planck -- can help guide model building in
models of the MSSM, split-SUSY, and beyond. Our model also demonstrates the
utility of UV models in constructing cosmological priors. (abridged)
