Dungeon Defenders is fairly unplayable on desktop Linux due to this bug: https://bugzilla.icculus.org/show_bug.cgi?id=5831

This bug is easy to reproduce and they even know the issue (lack of physx support on the linux drivers) and even though there's a workaround (Android version doesn't have this issue) the devs still haven't fixed it. They could at the very least stop selling new copies to Linux users on Steam until this is fixed.