I’ll echo a lot of what has been said. I was terrible with her in the CTT, and I didn’t really notice one way or the other in the Prologue since I was just itching to get into the real game.
I played against a killer Mellka one game (jumping all over the place, impossible to kill, crazy K/D ratio) and decided that I would have to give her another shot since I had just unlocked her. Parting Gift is great, as you can get several enhancements to it later in the skill tree. She’s great at diving deep, and her real strength is in rattling the other team’s cage. You can get in and do some real damage with abilities, or do just distract an enemy or two before retreating to heal up. I also have gear which gives enchanced movement speed plus extra speed if all skills are on cooldown. You can basically stick and move to keep the enemy at bay. She works great in team fights, and her melee actually works really well, particularly if you can get behind an enemy who doesn’t realize they’re backing up into you.
I don’t always do the best, but I would say 70% of my Mellka games, I have the most kills and fewest deaths on my team. She is a bit squishy, so you need to know when to stand and fight and when (more commonly) to retreat until backup arrives. I think she’s categorized as “easy” because she does decent damage with all attacks, and she has enough speed to run away from most other characters, making her really hard to kill if she’s paying attention.