TWWHD's Hero Mode is pathetic. The double damage aspect makes the game more even actually; in a regular run, Link is simply overpowered thanks to the abysmal damage that enemies deal. However, taking 1/2 a heart's worth of damage is still nothing to brag about. In a series filled with difficulty levels, I find Kingdom Hearts II Final Mix to be the cornerstone of difficulty. Taking double damage is meaningless if you still won't die often. However, if enemies are allowed to one-shot-kill you thanks to the amount of damage they deal to you in that higher difficulty, then it's something to run home and brag about.
Not finding hearts on the ground or in pots is nothing thanks to the poor damage ratio. Again, if there was actual danger in the game, then not finding hearts would be significant. But hey, I can still take around six hits on HM so it's no biggie :3
So my improvements would be to make the double damage aspect not be double damage, but instead an even higher ratio. Hero Mode as it is should've been the standard damage ratio, IMO. :/
Keep the no hearts dealio as a part of Hero Mode, not the regular playthrough.