You can take your hoe and a ton of stones and create a pillar of earth as high as it will go. You just stand at the top and kill him with range. Make the sledge hammer from the vendor too so you can just blast his adds away when they occasionally get summoned up there with you.

Anyway, I completely agree. The boss battles are something I dread because it feels like they are unfairly hard compared to what you can do and what you've been facing. The first boss is the only one I actually fight. Everyone else I cheese with the cheapest cheesiest methods known. Look up the boss fights on youtube and try out some of the strategies there.