I just had a game as the OKW (my first one after the patch) and I faced of against brits.
Somewhere in the mid-game I chose Special Operations as a response to the emplacement-heavy play of my opponent. Obviously I went for the Sturmtiger to deal with the mentioned emplacements. I had to witness one of my Shots taking away only 3/4 of a 17 pounder (not decrewing it). My Sturmtiger shell also failed to destroy a mortar position (decrewed it, but it barely survived). It's important to say, that none of these emplacements were barricaded when my shell hit.
I guess that's supposed to be that way? I am not sure. So the Sturmtiger is not a good counter for those? What do the strategists say?
And whats the best way to deal with mortar emplacements at spots difficult for me to reach with vehicles? Offmap maybe?

(The artillery barrage you get with the Panzercommander on top seemed to be quiet effective, though).