How good is a Manastone really?

[VincentVolaju]

Im a 15 Druid at the moment, and seems like one use of the manastone gives me around 3-4% mana but takes like 10-15% hp. I cant really see why this item is worth so much / so many people want it. I mean I know it doesn't drop anymore but, how good of an item is it really when the ratio's are so bad? I mean you spend more time and mana healing yourself from one use of the manastone that you end up with even less mana from before you even used it.

Is there ever a point where my heal will heal me for more hp then the hp cost of using the mana stone?