I think, Rohit played brilliantly, so did Virat & in their short stay both MS & RJ batted well - the issue is not their batting. Any given day, on a WACA wicket, 309 (regardless of 3 or 9 down) is a good total.
But here, IND was playing Australia - no one can predict, what this Aussie lineup is capable of chasing. They have Faulkner at 7 with 43/113 stats & Wade might bat at 3 for Pakistan, who comes at 8. In AUS, the closest team to them is SAF, who were crashed 4-1 just about a year back. Only way to beat these Aussies in AUS is to put them in, keep things tight & the Aussies 'll go for self destruction in some days, because they play only in top gear. In recent times (last 20 months) AUS had lost 3 ODI at home & NZ, if I can recall correctly - all 3 batting 1st & in all 3, they were all out well before 50 overs. In UK, they lost both the games batting 1st (1, I can recall), in UAE, "almost" lost an ODI, again batting 1st. Apart from IND in IND, I don't think any team can bat them out of the match, by posting a target - even then, Faulkner almost chased 383.
This is what I think went wrong for India & the blame goes to MS, Virat & Shastri. Being put in, AUS, might have ended 383/8 - that was end of it; but there was a sniff of chance that against 2 balls, IND might find them 90/4 after 15 & then Ash & Jaddu strangles the late middle order to submission; may be for ~300 sort of total, which could had been chased, particularly against this inexperienced Aussie attack. Batting 1st, in a day match in WACA, IND can put 375 - still I'll put my money on Aussies to chase that. They are head & shoulder above chaser, because of having the fire power to blast, the fitness & stamina to chase extra runs, couple of "the master batsman" to play 150 sort of innings, which is essential to chase anything over 330 & most importantly - unlike SAF or Pakistan, they don't choke, once they have the game between jaws, it's the end of it.
India has wasted 1 toss, now I think, it's going to be 5-0, unless, Aussies rest half the squad & MSD wins toss at SCG day-nighter; though Warner's loss is worth just a little pause ......