Build Auras, buff beam, reflects, pylon, and lightning towers first ontop of the bridge. (In the center of the bridge theres a crease do not build directly ontop of it just slightly off center, otherwise the boss will one shot the build.)
2nd wave complete the build and have your summoners with guardian pets sit under the bridge. (or monk heroes with guardian pets if you want to spear farm.)
Blue arrows are cloud directions and if your auras arent large enough just put them on the inside of the cores as apposed to outside.
I used a TB monk under the bridge during the boss wave. (You do not need a dps hero.)