The client-server lag realy needs a fix, but to me it does not look like a simple "the servers are far away u have lag" situation. i belive this lag problem is found in the server code to this game.

Most mmo games are set up with a Authoritive server approach (makes it impossible to cheat with maphacks etc, so most mmos are made with this method), which means the game runs on a server and not on the client u play, u simply play a copy of the game, and everytime u do something it needs to "sync" with the server the game actually runs on.
This results in what u call "input lag".
Lets say on the client u play u shoot a mob, the server (aka game) actually needs to listen for u to issue the "i shot a mob" command then run that, then send the result back to you "mob was shot".
this communicating back and forth from the server on every action causes "input lag" as you called it.

This is not server distance lag ! this would happen even if the server was in the next room. And most games that are made on the Autoritive server method, have a way of dealing with this called "lag compensation".
which basicly just means that instead of the client listening back from the server before it completes the action, simulates what would happen anyway on the client (client is a copy of the server side real game anyway) making it seem like there is no lag. aka removing the "input lag"

I dont know if this is the real problem (no clue how se codes theire games but there is no denying there is some massive server side code in there), but to me it realy does look like it (and i do work in the games business after all, as a artist tho, not a coder) and if it is, it is a coding oversight that should be fully possible to fix and even out.

And it realy makes this game not "feel" as comfortable as it should, and i belive fixing basic stuff like this , would make the rest of the game so much more enjoyable.

Tl-DR: the "input lag" is probably a codeing error, SE fix plx.