The root that comes from a leap does in fact mez you. That takes my ability to "act" away. Slows are fine - roots, mezzes and stuns are not.
I think what you are referring to is the interrupt that accompanies the leap. If we lost it as a baseline feature, I think I would be ok with that.
But leap most certainly does NOT apply a break-on-damage stun to the target. Some Jugg's will use their AoE mez after they leap into a pack to position for the Smash, but that isn't part of the leap.