As a Tony Romo supporter (when he does not

play the Giants), I have to agree with your assessment.  Tony R. can pile up pretty stats during regular season but he can't perform well under the spotlight.  He is indeed not a big stage quarterback.

Since Tony botched the hold on a game deciding field goal in Seattle back to 2006,

2007: the red-hot Cowboys team with 13 probowlers lost in the first playoff game to the Giants

2008: The Cowboys needed to win the last game to get into playoff but were blown out by the Eagles 44-6

2009: After winning their first playoff game in 15 years, they were humiliated by the Vikings 34-3 in Minnesota.

2011: The Cowboys could win the division if they could beat the NY team on Sunday night.  The NY Giants prevailed 31-14 however

2012: De ja vu.  The Cowboys came up short against the Redskins last night.  Again, on Sunday night  

Not all of failure were Tony's faults but he is the major part of the offense.  It is interesting to see how the Cowboys deal with him next season when his salary will be over 10+ millions dollars.