That's why we have potions that heal health. The hearts are merely there as a "blessing", they are mostly luck based and are already fine as they are now. The intended drop-to-heal ratios of hardmode in the game is fine as is. (Of course, it is assuming that these hearts have the same drop rate as a normal heart in hardmode. If they do drop rarer, then it would be pointless to implement. It would heal no faster than just two hearts dropped at once, which could prove interesting if balanced correctly.)