ok, further research made me feel better:
TMac age 25 (default league file)
A- A- B A C B
2005 Rockets 82 24,0 6,5 6,2 ,469 ,795 ,355
TMac age 26
A- B+ B+ A C B
2006 Rockets 82 24,4 7,1 5,5 ,455 ,803 ,411
2007 Rockets 82 26,0 7,1 5,3 ,476 ,770 ,425
2008 Rockets 79 25,9 7,7 5,0 ,481 ,764 ,411
TMac age 29
A- A- B+ A C C
2009 Rockets 82 24,7 7,0 5,0 ,464 ,788 ,387
2010 Rockets 73 25,5 6,9 4,0 ,476 ,814 ,387
TMac age 31 (prime ratings)
A- A A- A C D
2011 Lakers 77 27,3 6,6 4,2 ,461 ,786 ,425
2012 Lakers 75 28,2 6,9 4,1 ,491 ,766 ,447
2013 Lakers 82 29,0 7,4 4,3 ,478 ,776 ,442
TMac age 34
A- A B+ A- C C
2014 Clippers 81 24,2 6,4 10,1 ,474 ,806 ,427
2015 Clippers 77 23,4 6,4 5,1 ,473 ,776 ,453
TMac age 36 (last season)
B+ A- B B+ C F
2016 Clippers 76 20,1 5,4 5,1 ,445 ,835 ,376
Guess we don't have to expect superman then ...