When you do a rep recalc, that should update effected users' profiles to show rep before, rep after, and the time of the recalc on the profile page.
I don't find that particularly useful. 'Rep before' doesn't exist anymore after the recalc. 'Rep after' is shown in the profile anyway.
What might be useful is letting people know a recalc has been made on their accounts only, probably in the Recent tab, if only to reduce the surprise.
For a general recalc I think a notice on the blog would occur so again, no need to.