Quite right about LRMs in TC. I have a great deal of trouble with Longtoms. GECM mechs are dangerous as well, but the Catapult prime fares better than other LRM boats, especially since it has BHP to see them with. Once, in another game, I even took out a charging UAC loki by coring him with MBLs and jumping out of his line of fire while recharging. Just barely made it with a sliver of armor left. JJs are even more useful now than in 0.3...
Aeroes aren't as much of a problem on Marshes, since there are only VTOLs and even they are only available from the central base. On other maps, the Catapult still has JJs to avoid heavy aerial ordnance. Aeroes are still major threat, but not instant doom. Plus the Catapult's BHP means you'll get better advance warning of aero passes.
The best place for LRMs on Marshes that I've found is near the center of the map, with the wide open airstrip. Plus the VTOL landing pad can be used for reloads, even for mechs.