Since the discovery of slow relaxation of the magnetisation in paramagnetic metal-organic molecular clusters, various strategies have been pursued to enhance the performance of these so called single molecular magnets (SMM). On this route two key characteristics need to be optimized: The effective energy barrier Ueff separating the magnetic states should be large and the effect of quantum tunnelling (QTM) through this barrier is required to be weak. Over the past years, the synthesis and study of heterometallic 3d-4f complexes has attracted intense attention, because the combination of strongly anisotropic lanthanide moments and exchange coupled transition metal clusters hosting slow magnetic relaxation rates is expected to address both problems simultaneously. We performed spectroscopic studies on butterfly-shaped V(III)2Ln2 (Ln = Tb – Yb,Y) complexes using multifrequency high-field electron paramagnetic resonance (HF-EPR). Pronounced resonance features allow for precise determination of microscopic parameters such as magnetic anisotropy and interaction constants of the paramagnetic ions. We uncover that magnetisation measurements on 3d-4f butterfly complexes can easily be misinterpreted and discuss our results with respect to the dynamic magnetic properties showing SMM-like-behaviour in some of the studied compounds.