I don't really see any problem with having 6 hearts and upping the enemy damage. As stated by
Caelus before, it might be the same if we had 3 hearts with 1/2 damage each and 6 hearts with 1 damage each, but in the end, it'll make a huge difference -- 20 hearts with 1/2 damage means 40 hits until death, while 20 hearts with 1 damage means 20 hits until death.
Yes, this does mean less Heart Pieces and Containers, but what I think they'll do is add in
other collectibles to make up for it. In
Twilight Princess, we had 5 Heart Pieces to collect to make one heart, but we really only had Poe Souls and Golden Bugs to collect besides that. In
Skyward Sword, it already looks like we'll be collecting a lot more than just that.
It might not be tradition, but remember that following tradition is not always a good thing. 3 hearts in the beginning of the game with the average enemy doing 1 heart's worth of damage is
immensely difficult for new players coming into Zelda... And we can't forget about them.