Regarding underestimating qualitative methods: I'm actually all for them. It may turn out, it's all you need. (Maybe, a quantitative test will be required to prove your point, but it will probably not contribute much to a solution.) It's really that I think that A/B testing is somewhat overrated. (Especially, since you will probably not really know what you're actually measuring without appropriate preparation, which will provide the heavy lifting already. A/B testing should really be just about whether you can generalize on a solution and the assumptions behind this or not. Using this as a tool for optimization, on the other hand, may be rather dangerous, as it doesn't suggest any relations between your various variables, or the various layers of fixes you apply.)