I wouldn't say "overwhelming" I think india are definitely favourites due to home conditions and the massive quality gap in the openers. india's top 2 are the best in international cricket and sri lanka's are probably among the worst along with new zealand, even the windies have gayle, but things even out. I don't think that india's middle order is that much better, if at all, it just has the bigger names, but a look at the player rankings tells you that it's sri lanka with 2 middle order batsmen in the top 10 and india with none.
I think the last series isn't really relative anymore, it was over 3 years ago, before sangakkara was batting full time while now he's rated the best in the world, but more importantly, it was a few months before they came back from a test down and drew in england which was a turning point in sri lankan cricket.
as always with SL it depends more on certain key players performing whereas with india the match winners can be anyone so they do have the edge. Just wouldn't be surprised if sri lanka do it. they can score big totals and they have bowlers to trouble anyone.