Personally, I think Warne's Test (not ODI) career would be better split into five parts, not three. Let's see, there's his nervous, feckless debutant stage (4 Tests, Jan-Sep 1992, avg: 96.50), his 'first coming' (60 Tests, Dec 1992 - Feb 1998, avg: 22.84), his 'form slump' (34 Tests, Mar 1998 - Jan 2002, avg: 33.67), his 'second (disjointed) coming' (32 Tests incl. the World XI one, Feb 2002 - Nov 2005, avg: 21.08) and his 'fade into retirement' (15 Tests incl. Bangladesh, Nov 2005 - Jan 2007, avg: 29.72).
Note that I'm being entirely objective. For instance, he may have bowled well for little reward during his 'form slump' (ala Ryan Sidebottom until...oh...this month) and he may not have been as good as his stats indicate during his 'first coming' (though, by all accounts, he certainly was), which I was too young to really bear witness to.
Waqar's career is (to me) a little less straightforward, since I never got to witness him live. However, there's his nervous, feckless debutant stage (5 Tests, Nov 1989-Feb 1990, avg: 46.10), his 'superstar' stage (28 Tests, Oct 1990-Oct 1994, avg: 17.66), his 'fading star' stage (18 Tests, Sep 1995-Mar 1998, avg: 29.32) and his 'has-been minnow basher' stage (35 Tests, Mar 1998-Jan 2003, avg: 28.09 including minnows). So, I guess that I agree with you, there.