Piffle. RP Singh is, in my eyes, the most overrated of the current Indian seamers - that's really saying something, in this case. He's like a poorer left-arm version of James Anderson (wouldn't necessarily have said that he was poorer a couple of months ago). Given that I don't really rate Anderson highly (given his proven incompetence in non-swinging conditions against good batting line-ups), that's some stinging criticism, right there.
Sreesanth, Ishant, Zaheer are the three most ideal Indian seamers, for mine. Praveen Kumar may have shown a capacity to move the white ball, but moving the red ball, as people like Mitchell Johnson will no doubt tell you, is an entirely different business. I'd have him as backup.
As for Ishant Sharma, I wouldn't worry too much about his on-field form. Bowling well on roads does not necessarily lead to a bucketload of wickets, or, in the case of ODI's, a good economy rate (although you obviously have a better chance of attaining one if you bowl well). Irfan Pathan, particularly in the South African Test matches, looked toothless and bereft of any real pace. Ishant has shown an ability to bowl at far greater speeds with greater movement than Pathan, although both can be expensive.