Hm, does insta-kill work only from Curser's attack, or enemy units with low enough health just spontaneously combust to ashes when entering Curser's spere of influence? If latter, than wow, Eva's way too OP, gibbing some fatties with one-eight of their health intact.
...If former, than Eva loses half of her utility (disabled attack on skill) for way better defensive support for your front-liners.