I think 2h can beat shielders in a duel some times, but good thing its not a dueling game!
As shield I have helped the team (and multiplier) SO much more than a 2h or pole user. I can block 3 guys at once, distract half the team in a remote part of the map, push though an enemy formation, be part of a shield wall at a choke point (or be a 1 man shield wall sometimes!)
In this way, I think it is more powerful than 2h.