Hmmm, interesting. Need to check this again later, but for now Overheal seems somewhat counter-intuitive, in need of clarifications and maybe OP.
-No duration for the sickened/nauseated duration.
-At low levels it's basically assured you'll sicken/nauseate your own allies. You're better off "healing" your opponents.
-Then even when it works as a buff instead of crippling/killing, it's basically HP bloat, which is kinda bad in my book as it rewards casters and punishes mundane dudes trying to stab stuff to death.
There's also the part where this grants incorporeability with a 5 level investment and no drawback, while basically every other incorporeal creature around here either gains it slower or with strings attached.