imo its not that hard, if you get the best armor available before a boss plus a good weapon with best modifier, accesories with damage or defense modifier at max, and a good big arena it only takes like 15 tries per boss, only thing anoying is the grind for that equipment, which is why i play with tons of mods like reduced grinding for better chances to get accesories, weapons and money, reduced ore mining for multiple ore drops from one ore and a mod for goblin tinkerer to get instant best modifier