At long last AMazing TD is on Early Access.
It has been a long journey from Starcraft 2 Beta custom maps in 2010. That is when the first TD like this has been released. It changed lot since then, I hope you will like this version.
Some sneak peek of multiplayer:
The map is divided into two identical layout, you and your opponent can only build on one side. On higher levels there are areas which are shared and can be built on by both players.