The best counters for the pyro are the huntsman and another pyro. You ever see two pyros running into eachother, stop, and proceed to flamethrower eachother until they're both dead?
No, because I normally use more than my flamer to fuck the other pyro up. Flare gun, ax, air blast :D
Anyways, back to the intended topic. Mortar is fine the way it is, although additional push-back would be legitimate for making cover-whoring more difficult. Adding the additional push-back and it maintains its hybrid use of anti-infantry/anti-tank capabilities with the additional feature of making that comfy camp spot for carbine sluts harder.