Wow that sounds like one annoying experience for you....That seems to always happen with either Mara or Golden Hill KQ. Something like that rarely happens in King Slime or the other KQs from then on.
It really really is soooo frustrating when people just start going forth and getting no only themselves killed but all the others by dragging the aoe mobs behind them. It's so like UGHHH.
Next time, try to speak out, try to be the 'leader'. They need some leading hand, seriously. If you don't tell them, no, if you don't SCREAM at them what to do, they will always keep on dying.
That sounds horrible....hopefully it doesnt happen again.