Alright I don't want to be fair to the humans but the mk1 death cube... Is pretty impossible to the humans who do the hammer challenge...
just don't walk straight up it
p.s. I've found jetpack essential for the challenges :)
I lead everyone off the ramp and kill them there.
Tactics are important, it is designed to be a difficult challenge. :-)
Difficult challenge!? Maybe it's just me, but the bow only challenge was a living nightmare to beat.