Honestly, we had a difficult time deciding if this poll should be decided by a simple majority, rather than a super majority. When we first decided to start polling, the team decided that whenever we are making a major change to the existing game, that change should require 75% of the community to agree to it. We wanted to avoid anything close to a 51/49 split. Mixed Borderlands definitely falls under the category of a major change to the existing game. However, what made the decision harder, was that polling only started relatively recently. Had this poll existed 6 months ago, before we ever started rotating borderlands, it likely would have been decided by a simple majority instead.
This poll, along with almost every poll we have put up to date, has required a 75% majority. Interestingly, there wasn't really any outrage to this requirement until now, the first time the 75% lost.