The mortar bulletins work fine. I use the auto fire accuracy one which really ramps up the amount of hits it scores when left to its own devices near the front line.
I have seen people using the barrage accuracy one, which might be good if you are a ninja with mortar micro. I however am lazy with it and like it to score free hits while I micro other things.
I think the problems come if you stack mortar bulletins, this may cause strange behavior.
I dont know about the arty bulletins. Pretty silly to use as your warning your enemy to plan from the beginning to kill a howie.
