Defender you just have to have your super ready with WoL, and have all enemies downed so that youll have time to down him twice. If you repeat that process twice, he should be done for if not, try using a mox of heavy, special, and a grenade in between the two to knock his shield down. For sunbreaker, Scorched Earth is a great way to burn his shield down quickly. Use either thermite or Fusion Grenade to help with keeping his shield from recharging. The biggest problem with soloing him is time. You have to clear all of the adds (especially the wizards) and then down him twice. By rhe tome all adds are dead, you should almost have your super. If not, rockets and a fusion grenade should do the job