But if the 'loot-stealing' alts were present the he couldn't have been soloing it. If he was soloing, there would be no way for the alts to know when to connect/tp.
Most players will wait to collect loot from subcommanders, as they don't move or have a time limit. Considering that the alts only tp in at the last second, if they are already there before you origin, the subcommander would probably die before the alts could be moved away.
When the subcommander gets to lowish health, just back off and switch to a safe tank like Hercules or Fury. Nobody should really mind, and it's a piece of cake to stay in loot range while the subcom is finished.