I kept hearing that this quest was impossible to beat without using hacked/cheated weapons. To all the nay sayers it is beatable in a legit fashion.
Gave it a whirl with a fairly pumped up group and had trouble trying to beat it. Compared to Mu4 this quest seemed way more diffiult without using some massively P sphere pumped weapons. Well, we were determined to beat it the old fashioned way. After many failed attempts, which usually ended with us finishing the last wave and having the time run out at that exact moment, we finally managed to beat it with 19 secs to spare. The hunters of the group really need to be a high level. One hunter, level 186 was using a Charge diska with hit % work great here. The other a pair of hit mechs and a hit % diska. The Ra was using a spread needle and a pair of mechs. Me the force was using rafoie amps.
For others trying to beat this quest, you need to remeber where the dub witchs' spawn at and have a player waiting to pop it out of the sky asap. Many waves have enemies that appear near the team and some fairly far away. Having one player focusing on the distant enemies is important. Basic Cmode tactics for speed come into play here since every second literally counts for or against you.
Good luck on Mu3, its a worthy challenge.
