I feel mid-round tower placement is pretty important for the feel. At first, doing stuff like starting a wave and then spending a few seconds working out why I can't play the game is a bad feel that I only got out of because I knew some tower defence games lock you out when you're in the middle of a wave. That, and having something you can do mid-wave gives more to do.
There's a bug where you stop being able to block enemies entirely. I don't know how, but I put towers in a line on the bottom-left until eventually I could just place a frost tower right in the enemy's path and they just go through it, and at that point I couldn't block enemies any further.
The automatic wave timer doesn't feel necessary until there's the capability of multiple waves being on screen at once, and you can accidentally start two waves at once if you're foolish and click the next wave at the same time.
Power tier list:
A tier: Sniper / Poison / Wall
B tier: Everything else
Hard to really tier them right now without a lot of playtime.
Finally, I feel a 'randomize' option is sort of against the point of a strategy game like this. You might randomly win or lose waves depending on RNG with the same set-up but you might want to use randomize anyway for, say, poison. If there was an option that said "spread shoots evenly" / round robin I feel that'd be more appropriate if you can make it.
i enjoy crab