Well to be blunt, it doesn't and it's getting worked on. No amount of complaint or salt thrown at the devs on these forums or elsewhere will get it made any faster unless you can increase their team size magically. It's a bitter pill we have had to swallow, but swallow it we shall. Or we stop playing the game, which I'm not ever gonna do despite my personal gripes about the current state of the game.

Had a good few hours at the weekend but found myself constantly tweaking visual settings etc.
Did enjoy myself, but they really need to sort out optimisation so that it's more GPU heavy rather than CPU.

Yep. My current settings involve turning back on shadows (including movable) but at low or lowest values. It feels bad to not have shadows so I try to make up for it elsewhere. Then I drop resolution scaling to 91% and max out basic antialiasing at 3. It does take a very noticeable visual aesthetic hit but having shadows makes it worth it to me personally.

The age old problem I get with this game even since early release is when you have more players in an area, performance drops dramatically.