The game is very very difficult at the start and this might be a consequence of how stat scaling works. If everybody is close to 0, then a difference of 1 is a massive difference. It gets much easier as soon as you reach Lv. 10 and class change
The catacombs boss is so hard because, kind of like Dark Souls, combat in this game is a nightmare against more than 1 enemy. It would be one thing if he waited for you to kill the adds before returning, but he doesn't, and he spawns new ones as soon as the previous are gone.