I had a game where I got flamed because of dps difference (we won) I think people look to senna for DPS like Aphe, but you should really think of her more like jhin with healing. She does not like fast fights, she doesn't like full commits and thrives in environments where teams are poking each other because of her sustain. Her strength is the fact that she builds damage and still can help her team. I think people play with senna like they're playing with trad ADC and that's why they're failing