Why?
This game isn't fun when people turtle and build sim cities (admittedly, mainly a big team game issue) and it's less fun when people blob. Long range indirect punishes (and is the most effective hard counter to) this sort of play. It encourages smart infantry movement, aggressive play, and risk taking that makes the game a hellvua lot more fun than sitting your Elefant + Jagdtiger combo amidst a sea of bunkers and Panthers.
Idk if you mainly play Ostheer, but obviously that faction has some of the best defensive options in the game w/ MG42 bunkers, Pak-43s, S-Mine fields, Tellers, etc. Throw in a OKW Flak HQ and you have a position that is almost unassailable. There's need to be a counter to this and that's your Calliope, Walking Stuka, PWerfer, and Katy.
The rocket artillery is part of COH 2's gameplay. You'll punish with it and get punished by it plenty of times. Nothing wrong with it.
Now with all that said, the Calliope barrage is pretty devastating. I wouldn't object to it being a bit louder when it fires so Axis players have a better chance to react.
I had no bunkers, no pak43s, i had laid down a teller and S minefield. Had 1 pak 40 2 mortars 3 lmgs 2 mg43s pios and a scout car. I was hardly camping. The left side of the map where i was focusing was switching between myself and the USFs player right up until his 1 calliope barrage.
I wish that artillery was only used for cases like the ones you described.