Storage modulus gives information on the structure of the matter at various levels of organization, from molecular to higher. in this case, depending on the different levels of E' (or G') encountered, your results may suggest that CNT acted like filler but not reaching percolation yet.
1) Besides wt. fraction, the state of a nanofiller in the matrix (percolated or not) depends significantly on the filler dispersion state and polydispersity.
2) The modulus value itself does not mean much to judge about the structure. It should always be compared to the modulus of the unfilled polymer.
I agree with Evgeny's point 2). It tells you that it is stiffer, but you need to compare this with different loadings or the raw rubber. You don't say what loading you are applying. Different loading: tensile, compressive or shear may give different effects depending on the nature of the 'filler' and whether it is doing more than filling (i.e. reinforcing).