Proportionately the catacombs are very hard but the entire game isn't like that. You'll get stronger and stronger and towards the end of the game you will probably think yourself way overpowered. My suggestion for your problem is death scorpions, from the deadly gift skill. Just one or two of them will take out anything down there. Just don't get too reliant on them, you only get half experience for their kills. Also, a spammable spell like lightning works well. Once you get past the catacombs you're in for some real fun as the game takes off from there.
