You talk as though you have seen the client and server code... Fact is, unless you're a developer at FacePunch, then you know no more than I do about it. And stop talking bullshit about preprocessing... If you don't think it's my 680 being unable to handle the render calls, then you think it's my i7 and 16gb of ram being unable to process the pre render code? Stop pretending like you know what's going on under the hood. If it was client side lag, it would lag all the time... Server lag is dependant on load, which is normally at its highest in the evening, which, coincidentally is when it's most laggy. Unless my GPU and CPU decide to send half of its cores off to the pub for the evening causing client side lag.
I don't need to see the code, and it doesn't matter what specs you're running. I'm not saying your "amazing computer" can't handle the "preprocessing" or "render calls," which doesn't really apply because the game is not running on the bare-metal of your hardware, it has to go through the Rust client running on your machine. I'm saying the client software is unoptimized and can't take full advantage of your hardware. This is a fact, and has been stated by the developers numerous times.
And no, the client would not lag all the time. The client would lag when it had crap tons of data being rammed down its throat by the server. Which is what happens.
There have already been numerous threads about this exact subject explaining it, but apparently you either haven't read them or don't understand them.