Besides your fielding, your main problem is not having an all-rounder. Your having to either play 6 batsman, or 5 out and out bowlers, which leaves your tail exposed. However, if you play 6 batsman, your fifth bowler is going to be get hit around and taken for easy runs. You have to decide which is the lesser of the two evils. Personally, if I were coach, I'd prefer to play the extra bowler, Powar and Chawla have bowled well, probably your best bowlers in the ODI's so far, it'd make no sense dropping either of those two, and your top four, for ODI cricket should be able to chase most things down in general.
However, it's a longer term problem that either don't have an all rounder of the quality nessercary or your still waiting to see if Irfan Pathan can fill that void, or perhaps waiting for another youngster to come through.
Also, a fielding coach can imrpove your fielding, it can improve it vastly. Sri Lanka's fielding has improved immenseley since Tom Moody introduced Trevor Penny as their fielding coach, and it's obvious it's improve. South Africa's fielding has improved with the introduction of Jonty Rhodes, again, it's improve quite considerably. England's fielding has improved over the past few years, with the introduction of more fielding drills and practise. So clearly a fielding coach can improve your fielding, India just have the wrong man for the job, or the players don't want to improve, it's that simple.