I really like how Blizz made a community poll for S4 tier set bonuses. Whilst it could be improved, such as only allowing a lvl70 character of a particular class being able to vote only on that classes tier set and also making the poll available in-game. Not sure how the latter would work in terms of immersion but it could also be a mail vote with a quest attached or something like that.
Anyway, I think they should do this way more often to really get a steer on what the community wants and the whole community, not just the ones who read forums. In terms of which votes to release, this could either be ideas the development team have or based on a system where players can submit idea and the community gets to up/down that. Then each month, the top 3 progress to a full vote.