Re: how effective are the herders/dumpers?
 

To expand on what Brian Lucas said, the two dumper bots in the winning alliance at the Philadelphia regional proved to be really handy.

177 was the only robot that could score in the upper goal in our alliance, and during the finals, we lost our pneumatic system which made us unable to feed balls to our shooter. We made 1 shot during all of finals, but still won two matches. We used a good alternative strategy, and the other two dumper bots were responsible for all of the offense during those matches. with a little defense and ramping at the end, we still came up with a win.

Do not underestimate the capabilities of 1 point dumper/defensive robots.

Re: how effective are the herders/dumpers?
 

84 was just about the best dumper bot at philly, they also had a strong and reliable drivetrain! They almost pushed us sideways (which is a feat in itself) and if they had, would have dumped 30+ balls in the side goal... winning the finals. What scares me the most is that when they almost pushed us sideways, they only had 3 drive wheels out of 4... 84 was a very, very effective robot.