I personally believe that there is nothing wrong in having a foreign coach. John Wright was a foreigner but he has so far been the most successful of all the coaches we have had. Success or failure of a coach depends to a great extent on what values he brings on the table in terms of ideas. It is also important that he mixes well with the team members, prefers to remain in the background and boosts the players' confidence through proffessional advice.
It is true that even without a coach we are doing quite well. but the presence of a coach can take away a lot of burden from the shoulders of the senior players, who can concentrate more on their respective areas like bowling or batting.
With Dhoni being groomed as the future test captain, it is necessary that he gets all the inputs he needs from the coach and the senior players at this early juncture of his captaincy.
And for, heaven's sake let us stop blaming Tendulkar, Dravid, Ganguly or Laxman for all the ills of Indian Cricket. They have served the country well and are still quite valuable to the team, each in his own way.