Is there some reason why I can read this and find a problem with it and you can't?
Specifically the part about fireball does fire damage, but apparently snuffing out your life force does internal bleeding or negative energy damage. Correct me if I am wrong here, but don't we already have spells that do negative energy damage such as Enervation and Energy Drain. Fire damage is survivable, it does not cause death on a failed save. I don't know about you, but when a person saves versus fire, they are shielding vital areas from the brunt of the damage. There really is no way to do this when a death spell is cast upon you. The mere strain of actually resisting the spell causes damage, and failure to resist, well, it kills you.
Hmm...I wonder why all spells don't just do hit point damage? Maybe its a flavor reason, gee, I'm not sure.
Why don't all spells just become hit point damage? Everyone can be an evoker, but they'll have different names. How does that sound? You want everyone to be direct damage dealers with slightly different names? That is the vibe I am getting.
I'm sorry, snuffing out a life force is snuffing out a life force, not internal bleeding or negative energy damage. Internal bleeding comes from getting beat on with melee weapons or blasted with concussion spells. Negative energy damage comes from spells that blast you with negative energy. Death spells cause death on a failed save, not hit point damage. Dead, bye, bye. Say hello to my grandma for me, I dearly loved the woman. That is a death spell. Let the mechanic fit the name of the spell.