I had suggested a new set of war boosts which included a mortar that could release more poison bombs at a time at different locations for more damage. (In general discussions)
With the recent balancing, mortars are now surprisingly quite popular among top players as it resists max blizzard.
I do agree, storm cannons are way better than mortars for the same morale. I would rather keep a monk than 2 mortars which easily go down against a ranged troop. Although blizzard does not destroy it, it will lower its attack rate (which is already very poor). Maybe another update could make them overpowered.