New transport experiments on JET indicate that ion stiffness mitigation in the core of a rotating plasma as described in [P. Mantica et al., Phys.Rev.Lett. 102, 175002 (2009)] results from the combined effect of high rotational shear and low magnetic shear. The observations have important implications for the understanding of improved ion core confinement in Advanced Tokamak scenarios. Simulations using quasi-linear fluid and gyro-fluid models show features of stiffness mitigation, whilst non-linear gyro-kinetic simulations do not. The JET experiments indicate that AT scenarios in future devices will require sufficient rotational shear and capability of q profile manipulation.