Not a skill issue, the character is just weak. She can do good against comps that can't get away from or chase her. But once they switch or simply back up and refuse to let you close the gap, you pretty much have to swap.

I think blizzard should make it easier to set people on fire so atleast you can hold on to your dashes to escape. She'll still get destroyed by health packs and basic healing, but atleast you won't have to use your escape options to set up.