Will vouch for tilling. I got to the middle of year 2 without dwarf scroll 1 and it ended up being one of the last artifacts I found - got it by coming back to 15 repeatedly and using the iridium hoe charge up to mass clear the area for a few minutes. This is a good post to tag for remembering 55 and 95 as well though!
For what it's worth, you've already implemented my strategy for finding the last Dwarf Scroll: grumble about it on the forum, and it dropped a day or two later.
Related point: a great way to get the last Secret Note is to go to the trouble of planting a big field of pumpkins (or melon or cauliflower, depending on season), aiming to engineer a giant crop for the 100% Secret Note drop chance. The game will then mock you by dropping the Secret Note on the next thing you do...
For what it's worth, you've already implemented my strategy for finding the last Dwarf Scroll: grumble about it on the forum, and it dropped a day or two later.
Fate really does mock us with these things. I've had saves where it took multiple years to get a single Dwarf Scroll III and others where I had 4+ drop before the end of Year 1. I've never had that much trouble getting the other 3 Dwarf Scrolls, since I, II, and IV can all drop from monsters or from tilling (III only drops from monsters), but I'm not surprised that they do cause that much trouble as well.