I am in much better spirits as I'm writing this: thanks to some very helpful updates to Facepunch's Sprite Tools, I was able to optimize the file sizes for all of the sprites seen in the game. After reworking all of the game's elements to appear correctly with the rebuilt sprites, the game will now load in just a few seconds! If you were deterred from trying out the game before, I'd encourage you to give it a try now and see how it plays.
I'll see what I can do about updating the game to add new features. There is a lot I'd like to add (a leveling system, more than three classes with an ability to choose which ones to bring, items, and of course more enemy variety, to name a few), so if you like what's here so far, I'll try to add some more of those features, one step a time. Feel free to leave any feedback or suggestions: I've already gotten a few very good ones, so they will be what I do next.