They can also get doctrinal HEAT to counter doctrinal heavies.
A doctrinal answer inorder to fight a specific tank class on a tank destroyer seems pretty stupid. That's like taking the su85 and dropping its far pen to 150 and saying "just use ram + IL2, which is perfectly viable, just doctrinal vs non.
ontopic: HEAT rounds in general are super strong, maybe even OP, but I think as long as they're in the game the way they are people will always argue to use them over ever buffing the casemate TDs for axis. Furthermore, SOMEONE FIX THE JP4 VETERANCY.