Thanks for playing!
Yeah, i will have to investigate a bunch of of the issues you mention (graphical and sounds), they were already at the back of my mind for a while.
As for the graphical glitches, i know people on linux got them, i can't really debug it.. it's probably just a linux thing.
The enemies do hear you from behind, but only if you are sprinting; i guess i can make dashing count as well.
You should give wizard a try if you are having issues, i think it's the easiest starting class.