Experiments with negative ions in rotating superfluid 3He-A show strong retardation and deformation of ion pulses drifting parallel to the angular velocity Ω. This is caused by the interaction between the ions and the l texture in the soft cores of A-phase vortices. The interaction is mediated by the anisotropic ion mobility: v=μ⊥E-Δμ(E·l)l. The (Ω,T) dependence of the retardation is explained by a model that assumes focusing of ions into the vortex cores, along which the mobility μc is lower than that in the bulk liquid, μ⊥. We find μc=μ⊥-0.6Δμ.