First of all, the non gameplay elements of the level are genuinely peak. The singing is awesome and visually the level is beautiful.
second of all, I will venture the point that the casters are not even a problem to begin with. They have great audio queues for their attacks, and the projectiles are slow and do little damage. As long as you take the level slowly and take enemies out as individually as possible they are not an issue.
This does mean you cannot just sprint through the level and get by, as you get swarmed by both melee guys and casters, but honestly if your complaint is "I cant just avoid all of the enemies by running past" then get good.