Pfft, that 75 day level wasn't that difficult. You can always make it easier if you play the game at half speed. As with all RTS, single player difficulty = game speed.
Build 2 of each of the critical guilds: 2 warrior guilds, 2 ranger guilds, 2 healer guilds. Establish both northern trade routes after killing all of the level 1 spawns in the north. You'll be rolling in money. Form up parties. The bear-ish creatures will take down your buildings quickly, put cheap attack flags on them before they get close.
The demo is amazingly fun. I'm quite happy I had already pre-ordered a while ago.