I was using CW, DM, FM, Phoenix and DiB (assume Chapp can do the trick if you don't have it) first times I did 5.
You can play with something like that, CW was the one that survives more than all my tanks, maybe DW can do the job too (didn't have it at the time)
CW was mainly a meatshield that distracts a bit and resists a few seconds while DM was charging, sometimes reach second stage, usually not but his main job was only to protect DM at first 3-4 hits, maybe DW can do same job for you.
Then with DiB golem (or chapp heals) I could go through 2 and 3, sometimes DM died but achieve to beat 3, others had to retry as FM/Phoenix didn't do enough damge alone.
Keep trying combos, maybe your heroes haven't enough stars/gears, but if you put here all your rooster can try to think on a combo
