If you have a base with troll problems, dig trenches and build earth walls. They can't jump and they suck at ranged combat. And make upgrading your bow a priority unless you want to be a dead hero (well, you already are a dead hero, but you know what I mean). Anyone who fights an enemy on the enemy's terms deserves what they get (usually, a nice funeral). Eventually you'll get to the point where you can one-shot the big blue nuisances and then you'll feel sorry for them.