Have not tried a no bosses run yet. Need to perfect my 'Troll' mining skills first I think.

I'm currently on my "no portals - no bosses" run, and I'm having a lot of fun. You just have much more freedom, you don't have to follow a certain progression, but you still have to plan ahead, much more in fact then when using portals.

Troll mining is actually not that hard. Just get on one side of whatever you want to mine, let the Troll approach you and do a dodge roll backwards at the last second when it starts swinging.

Works for both copper and tin.

Iron is MUCH harder to mine, I just get enough so I can make the pickaxe. Silver is easy in comparison (even though you often get a visit from Mr. Stone Golem. Maybe even two).