I have been doing a lot of testing on island default and have found ways to cheese every single boss. Broodmother I use a megatherium (that is used throughout the run). monkey i do the same strategy that bishokukai uses. for dragon I use around ten hyeadons with about 300% damage plus the megatherium, i use a shotgun plus a dimorphdon to skip the fireball and spawning stages of the dragon. for the overseer I use a procopodon and a dimorph to first get through the tek cave easily (be careful of microraptors and yutys). there is a spot in the overseer arena that can be jumped to similar to the manticore on scorched earth. also for the snow cave and the cunning cave just do suicide runs if anyone is interested I can make some tutorials on the strategies.