Low Framerate, High RAM Usage

Observed in all window modes ('Windowed', 'Windowed Borderless', and 'Fullscreen')
OS : Linux Mint 18 - Sarah
BuildID : 1949708

The game is using 1.4 - 1.7 GiB of RAM, and lagging terribly; The title menu is sitting around 12-21 fps, in game menu 17-25 fps. Even the mouse has a noticeable latency, and there is near-constant screen tearing.
This is happening consistently, and appears unaffected by what I'm doing. As mentioned above, this even occurs in the pre-game title menu.
I have restarted the game numerous times, sometimes after restarting my computer, but the issue seems unaffected; however, today is the first time I've noticed this issue.

 

If it just started recently. I'd double check on your graphics settings, and perhaps any recent system updates if there were any.

In terms of low fps, and screen-tearing; I had a similar issue way back when the game first came out. It was resolved with turning Vsync on.
Might be something similar.