LoL if you say you can’t get past it with SP, you just didn’t try hard enough.
I’m solo-ing dungeons everyday in my hard difficulty SP and got some goods out of them, like free 50-100 black pearls per run or free premium items (2-3 per run). And fyi, i’ve just started playing this SP for more than 2 weeks.
Just build your base on top of the volcano, farm metal like crazy, get yourself at least 2 set of good stats flak, a good sword/pike (both is best), a good crossbow/compound bow, and a raptoring good pump shotgun (for medium-hard difficultly i meant). Then there come foods, 3x cant