This is one of the few games where where it feels like I actually level up faster the higher level I get (maybe the disparity between the slowness of combat at the beginning and the ability to dish it out a bit more once you have some stats built up). So I spent the vast majority of my time in game so far grinding the **** out of my paladin, my dog, and that Hugo guy; bouncing in between locations taking out any stray and/or respawned bad guys I could. Last night I just hit level 24, and I'm getting weary.

When should I try the mines?

lol I think you should be good to go. I'm not done with the mine yet but I started at around lvl 15-16 and I'm now lvl 20. I'm a few levels down now. I'm playing a ranger.. err thief so I dunno how you'll fair as melee but I can't imagine it's that much different. Pack a lot of pots and be prepared to make a few trips in and out of the mines if you intend to sell all the loot that drops.

Level 15 seems optimal for doing the non-Orcs levels of the Iron Mines. At level 14 you become Journeyman in Melee skill and at level 15 you can become Student in magic schools of your choice. This is when Light spell becomes available for your character, so you can light the dungeons which helps with fights and exploration.