Are heterolytic dissociations barrier-less or do they have an activation energy? When a bond is broken into ionic fragments, and I'm specifically thinking about organometallic or coordination chemistry, the two products carry opposite charges and the potential energy curve should, in my humble opinion, be attractive everywhere (at every point where the distance is larger than its equilibrium value).

Does this mean that the dissociation of a compound like ferrocene into $\ce{FeCp+}$ and $\ce{Cp-}$ (in the gas phase) occurs without a barrier?
In my theoretical research I have often seen that, indeed, there is no barrier for such reactions. In modeling the kinetics you take the bond dissociation energy as the forward barrier and assume a zero barrier going backward. This will also be true for radical recombination reactions.