Is wrecking a necessary assumption an applicable strategy for every question of this type?

If I'm not mistaken you're referring to the methods discussed in Causation Strategies:

For that I have...

Locating mistakes in the chronology of events

Blocking the 3rd common cause

The use of a competing data set

Finding a competing explanation (alternative hypothesis)

All four kind of blend into one another though, which is mentioned in the lesson.

I hope this helps! If anyone can add onto this or correct me, let me know!