2 suggestions to make Melissa an interesting hero
Currently Melissa's skill design is counterintuitive to the way PvP in this game is played, and makes her almost unusable in PvE due to Curse not affecting boss monsters. I believe these two improvements to Melissa would have a significant positive impact on making her a more viable hero:
1) Change Curse functionality to inflict damage to all enemies based on caster's attack when the cursed target dies
Currently, Curse's functionality in PvP is counterintuitive to how PvP is played - attacker heroes are sought to kill a target in one hit rather than leaving a target alive which may lead to uncertainty in securing a win condition. If Melissa happens to kill the target, Curse is functionally moot and serves no purpose in the match. These issues combined make her unfavorable compared to other heroes, like Cermia, which offer high single target damage with higher skill multipliers.
2) Grant Melissa innate lifesteal to assist in her survivability past her immortality buff.
Currently Melissa lacks functionality after her immortality buff wears off and without a healer to support her, or if she's faster than the healer and laps them, she loses immortality and quickly dies as a result. Giving her innate lifesteal would not only help remedy this, but also make her a viable option for fodder leveling in PvE (even without Curse impacting bosses), and allow her a bit of self sustain in PvP that may make the difference against difficult matchups. Not to mention that she's a vampire.