Can anyone diagnose what's going wrong if I do fine vs the first wave but die on the second?
well my diagnosis is err lack of info .
Firstly try and state what builds and weapons are being used , also i believe it should be nm.
There is a chance of failure - even small it does exist as i did 2 simulatanious runs using gwml and 2 accounts and weirdly the 2nd account had a few probs even tho exact same builds/weapons etc on both accounts and first account had no probs at all - and yes all heros were placed in indentical places.
beyond the lack of any info, you could be flagged wrong. dunno though. i used 3 mesmers with keystone builds and no runes and did fine. i parked my character in the back to grab aggro on destroyers before they attacked the dragon.
Is there a trick to keeping the heroes where you've actually flagged them? they keep running away from the rest of the group and getting themselves killed.