Here are the number of Receptions to RBs under McDaniels:
2005: 74
2006: 89
2007: 62
2012: 56
Here are the number of receptions to RB under O'Brien:
2009: 74
2010: 61
2011: 37
They both trend downward, but McDaniels still used the RB more than O'Brien. The reason for the trend downwards? In 2007, they Added Moss and Welker. In 2010, they added Gronkowski and Hernandez.
I think 50-70 receptions to RBs during the season, when you have the weapons of Gronk, Hernandez, Amendola, with the additions of Dobson, Boyce, Jones, Edelman and Ballard is about right..