Actually, when we have three wicket takers, we definately need someone who can apply the brakes to scoring. Who can apply pressure but need not rip through lineups. Take the Aussies, for example. McGrath doesn't aim for wickets, just keeps things tight. Even when he doesn't pick wickets, he is economical, and that is crucial. Similarly Ashley Giles slow-medium pacers are used to tie up an end against free scoring batsmen. Agarkar provides a good foil for Pathan, and lets Pathan bowl his natural game without worrying about runs conceded by his partner.
He is also a valuable lower order batsman.