Well lets look at the numbers and compare Garrett calling the plays and Callahan calling the plays and see how Romo has preformed under both.
2011........31 TDs...........10 Ints.............102.5 QBR (Garrett calling plays for season)
2012.......28 TDs............19 Ints.............90.5 QBR (Garrett calling plays for season)
2013........27 TDs............7 Ints...............98.3 QBR (Callahan calling plays through 13 games.........still 3 games to go)
I really dont see where you are getting that we had a much more aggressive offense with "monster numbers" under Garrett than compared to Callahan. Romo still has 3 games to play and he is only 1 TD behind his season total from last year and only 4 TDs behind his season total from 2011. Romo also has significantly fewer intereceptions with just about the same number of touchdown passes and his QBR this year is better than last season and only 4 points behind his 2011 QBR.
Anybody that thinks Romo is the problem with this team needs to seriously learn the game.