Stats entered are my own rounded down to the nearest 50th, im sure you can do with way less

First wave build all but gaurdian towers, drop mana with tb and build gaurdian mid wave

The only 3 towers I fully upgrade are Buff Beam, Nature Pylon, and Garudian Shrine (you probably can just get away with BB only)

2 heroes in till wave 10, TB and what ever else. Once wave 10 starts add in other characters you want to target farm and swap TB to HB
(For final wave I use 1 dps huntress w/ rifle, 1HB, 2 sword users[I use spin and builder gaurdian], this gives a nice spread of good weapons. Of course use what ever you are trying to target farm though)
 

Hints

1. Herm towers/gaurdian shield thingy placed on the upper part of the ramp

2. Owl stack placed on the lower level of the ramp
 

4. On last wave, swap TB for HB and bring down here at bottom of ramp behind wall so arrows cant cut, your huntress will be down here aswell to dps bosses. try to dodge arrows if you dont kill boss in 2 hawk shots

5. I have my 2 other target farm characters stand against wall here.