Filterbank based multicarrier modulations are well known to perform poorly in frequency selective channels when single tap carrier-by-carrier equalization is used. This degradation is cased by the inherent distortion in terms of inter-symbol and inter-carrier interference at the receiving side, which cannot be compensated via single-tap equalization. We provide here an asymptotic characterization of this effect. More specifically, we derive the asymptotic distortion after a single-tap perfect equalizer under the assumption that the number of carriers is asymptotically large.