Round Robbin is certainly not equivalent to random, and is much much better for most applications. If all the requests take about the same amount of time, then round Robbin will give the request to the one that hasnt received a request in the longest amount of time, which is clearly the best choice in this situation. Randomized has a 1/n chance of handing the request to this less busy node, which is why the problem becomes worse as you scale.