I think the problem isn't as much about the late game, big shot (somewhat) predictable weapons: Railway artillery, KV2, ISU152 etc. all have very high chances to wipe squads but they come rather late and one of their main purposes is to kill infantry.
Even artillery barrages tend to leave a good chance to escape unless the first shot is really spot-on. Other very strong wipe potential attacks just have a way to telegraph that something big is incoming (e.g. offmap artillery).
It is more about completely unpredictable behavior like your guys bunching up just the moment they activate a mine or a tank shot that would normally kill 1-2 guys suddenly killing 3-4.
It is also about cost: Something expensive (e.g. demo charge) and specialized (e.g. big slow tanks that are also not very good vs. tanks) can be justified to kill a whole squad
whereas a standard price unit that just has a tendency to get lucky (random overperformance) or a cheap unit (mine) should not wipe a squad without a chance to react.
For the most part I agree with you. The indirect fire system is unpredictable at best but it can be rather frustrating when you lose an entire squad on the move to the first mortar round out of the tube. I think that a metric preventing a wipe might be hard to implement however if there was some way to say is the squad static, yes, wiped whereas if the squad mobile 1-2 members lost. That would actually punish the units it is intended for static infantry.
In regards to mines I also see this as less of an issue as the game progresses I think I would prefer to see cheaper detection purchase on both CE and Pioneers lets say 15-20 that way defeating these systems with infantry only on the field would be more reasonable.
An additional but far more complex way to resolve this issue would be improving unit pathing.