I would use Thumper all the time, why bother with the others. 2 shells 2 minute cooldown. Enough for precision strike.
Because sometimes you want to level buildings ^^ and make big holes in the ground.
With all these artillery missions, you can actually remove all the artillery offmaps. So whenever someone offmaps, you have to "listen" for it in the background and its actually semi-realistic and penalises people with a popcap, mp and muni cost, instead of a WTFPWN ability that costs nothing.