Speed is a problem and being worked on. For now, the only thing you can do is to play using Firefox 58+ (https://www.mozilla.org/en-GB/firefox/channel/desktop/
), scroll down to Nightly then click on the platform you're using.
Are you using a hard drive disk (HDD) or solid state disk (SSD)? Using a SSD will increase your computer's performance greatly in general.
On desktop, you can switch to the old Flash version of the game, however games that use new Unity features (e.g. mods) wouldn't be supported.
As you are a member, you can download the standalone version of the game. See https://www.warzone.com/wiki/Standalone_Client
for details. The standalone app is loads faster than the browser version.
Edited 1/3/2018 14:59:48