Hey everyone,
This guide uses life towers to bank roll a bunch of life before hitting boss waves, so far I've only gotten to boss wave 2 but with some tweaking I'm sure others can get much further!
I've set it up in video format and the description goes over the element order. A quick note, this build doesn't fair so well with multiple people because others might end up downing waves much faster than you in the start, and you'll end up doing a lot of catch up in lives.
Best of luck!