I normally rag on QoT pretty hard. I've had pretty miserable results with her so far. But I played a couple 2v2 matches with her on Prison and we trounced.
One of her big problems is that she can either stay open and do OK damage while sacrificing survivability or she can stay closed and be wildly resilient while doing lackluster damage. On a big map with clearly defined lanes, this means she's going to pushed out more often than she pushes.
On Prison, she can leverage her teammate to shore up her shortcomings. Unlike the other maps, teammate is only ever 5 seconds away. Her teammate is the damage hose and she uses bramble shield to keep both people alive. In addition, it's now worth it to change forms and open up to access her AoE attack. With two DGs piling on the hurt, the armor reduction really shines.