I completed it after numerous attempts.
Here are some things i noticed/did. Having one group of blues and one group of greens is a bad idea, apparently the other teammates blues will be unable to heal the other teammates greens.
Instead i chose a different method. The first person grabs twenty greens then hides in the apprpopriate corner, the other teammate bashes some green bugs with browns (five green orbs per bug), restocks on health, grabs the greens then goes in the corner as well. Now you have fourty greens.
Positioning the greens is important. When jumping they might get over excited and start breaking barrels. That is the last thing you would want as it draws the attention of the dwarves. This might be bearable at first but later on you wont be able to cope with the staggering amount of dwarves that gather.
The rats come in waves every five minutes on the dot, fourty five minutes equates to nine waves.
After roughly five attempts i gave up on that corner, the dwarves would always find us when the rats came. Combinations of ten blue and ten green did nothing to improve the situation. My buddy and I instead hid in the corner closest to the green and blue spawn pit, broke all the barrels and hid behind the pillar with our fourty green minions.
The enemies in this area are alot slower and seemingly will not be able to reach you before all the rats have been dealt with, so they will wander off.
I'm casual