Sheep love to be led, and history has shown that they will follow a thief just as easily as they follow the real shepherd. Even the title of shepherd can become a temptation to rival the Chief Shepherd. This is what is behind the Catholic doctrine of the priests being literal substitutes for Christ. Of course character is also important for the sake of example, both to the congregation and to outsiders. The title of elder appears more commonly than either bishop or deacon, and is better defined in its duties.
Elders are the representatives and leaders of the congregation, who act in concert with apostles.
It is important that this title is used in the plural, and I believe that much of the extent of Nicolaitanism in the Church can be traced to the idea of one pastor leading worship and being the only one who speaks. Once this is in place, the pastor starts to become a priest, and the rest of the congregation falls asleep, content to passively receive his teaching. Of course there needs to be some control of teaching, or else heresy will flourish, but this can be accomplished without putting one pastor on a pedestal above the rest of the congregation. Certainly the most important thing for pastors to remember is that they are not priests, or rather that their priesthood is no different from that of the other believers. They are not here to worship for us or interpret the Bible for us.