Feb 27th 2008 2:00AM Honestly?
If they were to nerf it, and say.. Take 20% of your max health to return 15% of your max health AS MANA..
This prevents the scaling problems, still makes it health expensive, still makes it risky.
In addition, however, add a threat reduction component, so that while a far riskier idea in PVE than it was previously (For me, double the health loss) it does not drastically reduce the significance of the ability in PVE.
Alternatively, add a cooldown.
Lastly, and I think this is my personal favourite.
Add a 30 second cooldown, leave it instant.
Re-jig it, so that it costs 10% of health, and 10% over 30seconds (Yes! it could kill you) in return for 20% of mana over 30seconds.
Increases the risk factor. Impacts (Greatly) the utility of the ability in PVP. Leaves it slightly riskier, but for a better return, in PVE.