First of all, the boss is great. It's simple but it works surprisingly well and has a really cool design.
Although, I really think the lack of custom sounds for Toastmaster is a problem. I know he's a reskined Skeleton King, and he just uses his same sounds (laughs). A bit disappointing, because the map has various sounds and bits of custom music.

You should consider creating more unique custom sounds for Toastmaster (things like mechanical sounds and such) maybe even the boss can have his own voice. That would be amazing.