My most recent character, a non-warrior lowbie goodie, has been fighting Centurions solo since my thirtieth rank. I've had only one other with me while we cut through four roadblocks on the way to the Vanquisher (all were covered with the black shroud). I'll be the first to admit that Centurions are annoying, but they are not hard and they are not overpowered in my opinion. They're also a good distraction for certain Imperials who (I think, since I've never played an Imperial) are beckoned to the place where the Centurion is being attacked, thus providing a clear shot to raid the cabal. I think out of all the dozens of characters I've played, I only ever paid a Centurion once. The rest just either slew them or found a way around (which is not that hard if you explore surrounding areas).

However, I don't think they should be able to stop newbies (up to level 10). Though the toll is low, I would imagine a new player exploring the Eastern Road for the first time and not being able to figure out how to get around a Centurion. Also, I don't recall if they stop them or not, but I don't think a Centurion should be able to block a ghost.