Any fight that has adds that die relatively quickly and spawn periodically you wanna take War Machine for sure. As far as cleaving "multi-target" I wouldn't run Wrecking Ball or Bloodbath with less then 3 mobs. The lego belt is also a big help if your running Wrecking Ball.
Check the guide, but in short: on 2 targets only WW to make your rampage cleave, on 3 targets replace FS with WW and on 4 targets replace RB with WW, unless you have t20 4p, then just stick with the same rotation as on 3 targets, as in: BT, RB, WW.