So this isn't my picture, it's from Seatin's Twitter:

A few other people have posted similar pictures on Mephisto's spotlight thread. It seems to be an issue with the unique synergy between Mephisto and Dr Strange, which is supposed to increase his life steal by 70%, and appears to be over-achieving.
Whilst fixing this, how about:
(1) increasing our beloved doctor's extremely low base life steal? We've all wanted it to get a boost; but I admit increasing it to a million is slightly overkill.
(2) making the Sorcerer Supreme immune to having his soul stolen would be welcome too; just because he's, you know, the darned Sorcerer Supreme, and should have arcane defenses against that sort of attack.
Feel free to move this to Comments and Suggestions, but this seemed the right place to start.