Titans had begun to decline in  writing quality after George Perez left the series (and I recall Marv Wolfman commenting that he suffered some writers block during the same period). The erasure of Wonder Woman from continuity and the subsequent de-emphasis of Superman's Kryptonian roots (Kandor etc.) certainly had an impact on Wonder Girl especially and Nightwing tangentially but it was never a big issue for the series and the WG stuff wasn't even addressed for another four years.

The Legion didn't immediatly suffer as a result of Crisis.  Remember, the specifics of the Superman relaunch weren't known when Crisis ended, the next to last page of Crisis #12 had Superman and Power Girl walking off together in mourning toward the Fortress of Solitude.

Crisis's problem IMO was that the aftermath hadn't been worked out very well in advance.  Editors and writers were either unable or unwilling to get on board with the thing.  Result: a mad scramble after the fact to try and smooth out the wrinkles.  Compare the characters featured in Crisis 11 & 12, to what we got for the next 12-24 months.  My feeling at the time was if Marvel had done the same type of story, the transition to a 'new' Earth would have been much smoother.  Of course, for the longest time that was the major difference between the two companies, while DC had editorial fiefdoms which rarely crossed paths, Marvel prided itself on a clear editorial policy across its line.

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I recall a DC editor, years ago, saying that "Writer's Block is when you can't write, not when you write badly." Was he referring to Wolfman's troubles? I can't say.

Of course, one of my favorite quotes on the subject came from Charles Schulz: "Writer's Block is for amateurs."