I feel like you are meant to take every advantage you can think of to fight the bosses. I built huge earth towers to fight the swamp boss. I dug tunnels beneath the summoning alter to fight the mountain boss. I walled in the entire area to fight the plains boss. Actually that one was the most legit fight I did and let me tell you I felt like a god when I killed it.
I'm just saying that anything you can do within the game is fair play. No such thing as cheese here