And they should be, doctrines are supplemental to playstyle, map and what opponent does, they aren't supposed to be magical "upgrade" button to whatever you do regardless of circumstance.
Yes but given it's highly situational nature it's a risky investment of resources which will probably not pay off in the long run. As far as I'm concerned only people that want to meme use it or they've already won the match so there's really nothing to lose even if it's destroyed.
I'd rather take a StuG III E with an MG42 any day of the weak over the Sturmtiger.