I have given the issue a great deal of thought along the same lines as you ("how is a consequentialist to vote?") and concluded that it is extremely unlikely that voting is a good use of my time (not that my time is of any particularly great use) even taking into account the secondary benefits like fixing the imbalance in voting demographics (I'm young) or that my voting either way increases the nebulous confidence in our democracy since it increases voter turnout.

That doesn't mean I think everyone shouldn't vote-- for one thing, the fewer people vote, the more this arithmetic changes, and for another people get a lot of personal utility out of voting, from being satisfied with themselves and the social capital from showing others they voted. But I definitely wouldn't take the time to vote, and I'm not inclined to encourage others to either.