Feed back from a long time ARPG fan.
Rewards should highlight around the barrels at the end to help you notice they are there. I missed the first handful of rounds not noticing them.
Once you unlock a certain wave level like 60 on a character it would be nice to be able to just go right back to 60 with my next key and continue to work on progressing instead of having to regrind the relatively useless early levels. Just slapping things down in one shot is only fun for so long and feels like a waste of time. Thinking of something like Greater Rifts set up in Diablo 3, dont want the timer or anything just the ability to go right back to where they killed me and take revenge or being able to select any level 1-60 to start at since I have unlocked that difficulty.