If you are sexually harassed, and HR doesn't do anything about it, you should sue. Don't expect HR to change. If the stories in this article are true, and if the evidence is as strong as the article says it is, this is a slam-dunk case for sexual harassment, hostile work environment, retaliation, etc.
Suing would have lots of negative consequences, and few upsides. It would take up months of time, be immensely frustrating, stressful and lead other employers to be wary of you in future (even if most wouldn't admit it). Your name would be dragged through the mud by Uber in an attempt to derail the case, and you'd become an online target for haters (as with Ellen Pao). All for some uncertain monetary reward. Who need…
You have summarized a number of reasons why I would never ask anyone to volunteer to be the one to accomplish this.
This entire episode will hopefully shine some light on the true difficulties that need to be overcome to promote STEM diversity.