Kunal priority is to develop complete third leg of the trident for delivery of nukes, for that we need boomer subs that will deter the enemy (nuclear powers) that they will take unacceptable damage, for that we need ATVs with more nukes and missile on board.
As far as hunter class is concern yeah we defiantly need those hunter class subs, with their speed and endurance they will hunt down enemy boomers. but country like us cannot have that kind of luxury therefore we have to do away with ATV 1 which is multipurpose sub with small nuclear payload and semi hunter class features (you may say best of both worlds).
Indian depleting Submarine force need Indigenous boost, If India need to be a global power it needs to think beyond South Asia, for that we cant depend on mass imports ( Not suitable for country's economy ) 6 scorpions ( Not induced ) and -10 kilos cant be called as main submarine force, Besides India can operate only three nuclear subs in Indian Ocean by 2011, In this kind of situation India need to develop Indigenous Submarine force of ( 2000-3000tons ) mainly nuclear, Small Nuclear hunter killer class have low maintenance and service costs than their bigger boomer class..
For example i find freanch Barracuda_class as a good Nuclear Hunter killer sub!
http://en.wikipedia.org/wiki/French_Barracuda_class_submarine
Btw, Your Point is perfectly fine too, 47,000hp/70MW reactor and propelling 6000ton at 24 knots (44 km/h) (submerged) is magnificent!
1) Chinese huge armada of Subs are the spearhead of Chinese navy in Indian ocean..
2) Few ASW aircrats can only be use to defend the costal regions of India..
3) Sending bigger destroyer and Frigates in open is a risk..
4) If future India would need more Subs than surfaces combatants..
Btw, Sagarika is still developing and we may see a better one with good range in near future..
Any updates on Agni-3 Sub variant?