In one swamp I had bizarrely fast spawns for some reason, and ran into issues. I ended up just building a raised wooden walkway all the way through most of the swamp.

Used the short verticals as feet, so it's just barely off the ground. Mobs on foot can't seem to get on top of the platforms, son only ranged units (skels and draugur) were an issue.

Every once in a while, I built stairs up to a higher 2X2 platform, then stairs down on the other side, and continued the walkway on father. I shoot from the top of the higher 2x2.

Later on I saw a guy basically doing the same thing in a video, except he was just using the hoe to make a flat leveled walkway all the way through the swamp. Doh. Never thought of that, that person (which I cannot remember) is a genius.