Dhoni is a unique player. He started out as an out and out slogger in cricket, and was quickly sorted out by the opposition in regards to his deficiencies which were glaringly obvious. Thanks to the fact that India found a bunch of youngsters who could do a similar damage in the middle order like him, India needed someone in the middle who could shore up things when trouble ensued.
Agreed, his SR has come down from the lofty perches when he debuted. But his averages and overall addition to the team has soared ever since he switched to the Bevan mode as you suggested. This is evident from the figures below.
Code:
As Matches Runs Avg SR 100s 50s
Captain 51 1908 57.81 85.1 1 16
Not captain 84 2477 44.23 96.26 3 14
Those are exceptional figures, and his SR despite the accusation that he has slowed down considerably after becoming captain is still a very much creditable 85. And his consistent run with the bat is what has ensured India tremendous success in ODIs of late. I think India needs Dhoni of today than Dhoni of 2004/05, and that's precisely what he is delivering.