OK.
I still think they are too punishable once vet and weapons upgrades kick in. In case of mortars, i think their offensive performance is fine atm, it's just a matter of adjusting the cost and making vet actually matter.
I mean, the last tournament saw in every game basically 2x MG / 2x AT gun in both sides and no one bother getting a single piece of indirect fire (at least from what i remember and i checked rapidly the all finals and semis)
I would interpret that as a sign that mortars do not do enough damage because they have a hard time hitting stuff in the more mobile gameplay of 1v1. MGs also do not get RA, yet they are used. So I assume the lack of RA in veterancy is not going to fix that mortars are underused in 1v1 and in my experience also 2v2, especially considering that they are in a much safer spot that MGs by default.
They cost as much as mainline infantry but cannot do much on the defense, need a lot of scouting/planning and micro on the offense and additionally are bad for capping points. And if you the majority of your army got pushed back to base, your mortar becomes useless since it needs a forward spotter. Plus late game they are a prime target for rocket artillery if there is no other suitable target around. Yes, there is smoke etc, but in the end in 1v1 another mainline infantry seems to be the preferred choice.
The only unit that gets 1v1 play is the pak howie, I assume this is because of the good AoE. If we don't want to buff damage, the cost decrease could be a bit of help but I assume it is not enough. Another possibility would be to additionally decrease pop cost so that it is easier to fit them into builds also in the late game, although this might lead to spamming in larger modes (which however would make you more vulnerable to rocket arty, so might not be an issue).