are such rationality techniques very useful for really hard scientific problems...?

I now think that this was hyperbole. It seems obvious to me that the first and second fundamental questions of rationality are of fundamental importance to science. Namely:

• What do I think I know, and why do I think I know it?
• What am I doing, and why am I doing it?

The first question is essential for keeping track of the evidence you (think you) have, and the second question is essential for time management and for fighting akrasia, which is useful to those scientists who are mere mortals in their ability to be productive.

Rationality won't magically solve science, but it clearly makes it (at least slightly) easier.