No.
Only the AT gun (forgot the name) isnt useful as it costs way too much and its to easy to decrew.
Rest is fucking useful lol 
Well, next patch they aint go abandoned anymore, but actually the 17 pdr is more durable and sometimes useful, so it costs more. but anyways the rest are rather useless cause they cost too much and get killed too easily and u simply have no indirect fire to counter mgs and static positions.
Thanks, that one 
I've only build it 3 times and I was seriously disappointed how easy it is to kill that thing.
like u say, it's too easy to kill the emplacements and 17 pdr is the more durable than bofors and mortar pit, so those two are even easier to kill and not only the cost too much, but take way too much pop cap