MV performance regression

EC2 RF=3 (i2.2xlarge, also tried on i2.4xlarge)
mvn exec:java -Dexec.args="--num-users 100000 --num-songs 1000000 --num-artists 10000 -n 500000 --endpoint node1"

3.0.0-beta2 (alpha2 java driver)
-----------
total
             count = 461601
         mean rate = 1923.21 calls/second
     1-minute rate = 1937.82 calls/second
     5-minute rate = 1424.09 calls/second
    15-minute rate = 1058.28 calls/second
               min = 1.90 milliseconds
               max = 3707.76 milliseconds
              mean = 516.42 milliseconds
            stddev = 457.41 milliseconds
            median = 390.07 milliseconds
              75% <= 775.95 milliseconds
              95% <= 1417.67 milliseconds
              98% <= 1728.05 milliseconds
              99% <= 1954.55 milliseconds
            99.9% <= 2566.91 milliseconds


3.0.0-rc1 (alpha3 java driver)
---------

total
             count = 310373
         mean rate = 272.25 calls/second
     1-minute rate = 0.00 calls/second
     5-minute rate = 45.47 calls/second
    15-minute rate = 295.94 calls/second
               min = 1.05 milliseconds
               max = 10468.98 milliseconds
              mean = 492.99 milliseconds
            stddev = 510.42 milliseconds
            median = 281.02 milliseconds
              75% <= 696.25 milliseconds
              95% <= 1434.45 milliseconds
              98% <= 1820.33 milliseconds
              99% <= 2080.37 milliseconds
            99.9% <= 4362.08 milliseconds